Kdjykuj

I override appcodeMagentoProductVideoviewadminhtmltemplateshelpergallery.phtml file following below steps.

1) Create module name appcodeHsMageenhancement.
2) Create event.xml file under appcodeHsMageenhancementetc folder.

3) Added below code.

<?xml version="1.0"?>

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">

    <event name="catalog_product_gallery_prepare_layout">

        <observer name="change_template" disabled="true"/>

        <observer name="admin_product_gallery_change_template" instance="HsMageenhancementObserverChangeTemplateObserver" />

    </event>

</config>

4) Create observer.
Added folder Observer and add php file named ChangeTemplateObserver.php define in event.xml file
Add below code into it.

  <?php

   namespace HsMageenhancementObserver;

   use MagentoFrameworkEventObserverInterface;

   class ChangeTemplateObserver implements ObserverInterface

   {

      public function execute(MagentoFrameworkEventObserver $observer)

    {

        $observer->getBlock()->setTemplate('Hs_Mageenhancement::helper/gallery.phtml');

    }

  }

5) Added template file under
Hs/Mageenhancement/view/adminhtml/templates/helper/gallery.phtml
Copy file content from
appcodeMagentoProductVideoviewadminhtmltemplateshelpergallery.phtml

Added related_tire_price custom field into exiting code.

    <?php

/**

 * Copyright © Magento, Inc. All rights reserved.

 * See COPYING.txt for license details.

 */



// @codingStandardsIgnoreFile



/** @var $block MagentoCatalogBlockAdminhtmlProductHelperFormGalleryContent */

$elementName = $block->getElement()->getName() . '[images]';

$formName = $block->getFormName();

?>



<div class="row">

    <div class="add-video-button-container">

        <button id="add_video_button"

                title="<?= $block->escapeHtml(__('Add Video')) ?>"

                data-role="add-video-button"

                type="button"

                class="action-secondary"

                data-ui-id="widget-button-1">

            <span><?= $block->escapeHtml(__('Add Video')) ?></span>

        </button>

    </div>

</div>



<?php

/** @var $block MagentoCatalogBlockAdminhtmlProductHelperFormGalleryContent */

$element = $block->getElement();

$elementToggleCode = $element->getToggleCode() ? $element->getToggleCode() : 'toggleValueElements(this, this.parentNode.parentNode.parentNode)';

?>



<div id="<?= $block->getHtmlId() ?>"

     class="gallery"

     data-mage-init='{"openVideoModal":{}}'

     data-parent-component="<?= $block->escapeHtml($block->getData('config/parentComponent')) ?>"

     data-images="<?= $block->escapeHtmlAttr($block->getImagesJson()) ?>"

     data-types="<?= $block->escapeHtml(

         $this->helper('MagentoFrameworkJsonHelperData')->jsonEncode($block->getImageTypes())

     ) ?>"

>



    <?php

    if (!$block->getElement()->getReadonly()):

        ?>

        <div class="image image-placeholder">

            <?php /* @escapeNotVerified */ echo $block->getUploaderHtml();

            ?>

            <div class="product-image-wrapper">

                <p class="image-placeholder-text">

                    <?= $block->escapeHtml(

                        __('Browse to find or drag image here')

                    ); ?>

                </p>

            </div>

        </div>

        <?= /* @escapeNotVerified */ $block->getChildHtml('additional_buttons') ?>

        <?php

    endif;

    ?>

    <?php

    foreach ($block->getImageTypes() as $typeData):

        ?>

        <input name="<?= $block->escapeHtml($typeData['name']) ?>"

               data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

               class="image-<?= $block->escapeHtml($typeData['code']) ?>"

               type="hidden"

               value="<?= $block->escapeHtml($typeData['value']) ?>"/>

        <?php

    endforeach;

    ?>

    <script id="<?= /* @escapeNotVerified */ $block->getHtmlId() ?>-template" data-template="image" type="text/x-magento-template">

        <div class="image item <% if (data.disabled == 1) { %>hidden-for-front<% } %>  <% if (data.video_url) { %>video-item<% } %>"

             data-role="image">

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][position]"

                   value="<%- data.position %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

                   class="position"/>

            <% if (data.media_type !== 'external-video') {%>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][media_type]"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

                   value="image"/>

            <% } else { %>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][media_type]"

                   value="<%- data.media_type %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <% } %>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][video_provider]"

                   value="<%- data.video_provider %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][file]"

                   value="<%- data.file %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][value_id]"

                   value="<%- data.value_id %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][related_tire_price]"

                   value="<%- data.related_tire_price %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][label]"

                   value="<%- data.label %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][disabled]"

                   value="<%- data.disabled %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][removed]"

                   value="" class="is-removed"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][video_url]"

                   value="<%- data.video_url %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][video_title]"

                   value="<%- data.video_title %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][video_description]"

                   value="<%- data.video_description %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][video_metadata]"

                   value="<%- data.video_metadata %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>

            <input type="hidden"

                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][role]"

                   value="<%- data.video_description %>"

                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"/>



            <div class="product-image-wrapper">

                <img class="product-image"

                     data-role="image-element"

                     src="<%- data.url %>"

                     alt="<%- data.label %>"/>



                <div class="actions">

                    <button type="button"

                            class="action-remove"

                            data-role="delete-button"

                            title="<% if (data.media_type == 'external-video') {%>

                            <?= $block->escapeHtml(

                                __('Delete video')

                            ); ?>

                        <%} else {%>

                            <?= $block->escapeHtml(

                                __('Delete image')

                            ); ?>

                        <%}%>">

                    <span>

                        <% if (data.media_type == 'external-video') { %>

                        <?= $block->escapeHtml(

                            __('Delete video')

                        ); ?>

                        <% } else {%>

                        <?= $block->escapeHtml(

                            __('Delete image')

                        ); ?>

                        <%} %>

                    </span>

                    </button>

                    <div class="draggable-handle"></div>

                </div>

                <div class="image-fade"><span><?= $block->escapeHtml(

                            __('Hidden')

                        ); ?></span></div>

            </div>



            <div class="item-description">

                <% if (data.media_type !== 'external-video') {%>

                <div class="item-title" data-role="img-title"><%- data.label %></div>

                <div class="item-size">

                    <span data-role="image-dimens"></span>, <span data-role="image-size"><%- data.sizeLabel %></span>

                </div>

                <% } else { %>

                <div class="item-title" data-role="img-title"><%- data.video_title %></div>

                <% } %>

            </div>



            <ul class="item-roles" data-role="roles-labels">

                <?php

                foreach ($block->getImageTypes() as $typeData):

                    ?>

                    <li data-role-code="<?= $block->escapeHtml(

                        $typeData['code']

                    ) ?>" class="item-role item-role-<?= $block->escapeHtml(

                        $typeData['code']

                    ) ?>">

                        <?= $block->escapeHtml($typeData['label']) ?>

                    </li>

                    <?php

                endforeach;

                ?>

            </ul>

        </div>

    </script>



    <script data-role="img-dialog-container-tmpl" type="text/x-magento-template">

        <div class="image-panel" data-role="dialog">

        </div>

    </script>



    <script data-role="img-dialog-tmpl" type="text/x-magento-template">

        <div class="image-panel-preview">

            <img src="<%- data.url %>" alt="<%- data.label %>" />

        </div>

        <div class="image-panel-controls">

            <strong class="image-name"><%- data.label %></strong>



            <fieldset class="admin__fieldset fieldset-image-panel">

                <div class="admin__field field-image-related-tire-price">

                    <label class="admin__field-label" for="image-related-tire-price">

                        <span><?= /* @escapeNotVerified */ __('Related Tire Price') ?></span>

                    </label>



                    <div class="admin__field-control">

                            <input type="text"

                                    data-role="image-related-tire-price"

                                    data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

                                    class="admin__control-textbox"

                                    name="<?php /* @escapeNotVerified */

                                    echo $elementName

                                    ?>[<%- data.file_id %>][related_tire_price]"><%- data.related_tire_price %></input>

                    </div>

                </div>



                <div class="admin__field field-image-description">

                    <label class="admin__field-label" for="image-description">

                        <span><?= /* @escapeNotVerified */ __('Alt Text') ?></span>

                    </label>



                    <div class="admin__field-control">

                            <textarea data-role="image-description"

                                      rows="3"

                                      class="admin__control-textarea"

                                      name="<?php /* @escapeNotVerified */

                                      echo $elementName

                                      ?>[<%- data.file_id %>][label]"><%- data.label %></textarea>

                    </div>

                </div>



                <div class="admin__field field-image-role">

                    <label class="admin__field-label">

                            <span><?= $block->escapeHtml(

                                    __('Role')

                                ); ?></span>

                    </label>

                    <div class="admin__field-control">

                        <ul class="multiselect-alt">

                            <?php

                            foreach ($block->getMediaAttributes() as $attribute) :

                                ?>

                                <li class="item">

                                    <label>

                                        <input class="image-type"

                                               data-role="type-selector"

                                               data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

                                               type="checkbox"

                                               value="<?= $block->escapeHtml(

                                                   $attribute->getAttributeCode()

                                               ) ?>"

                                        />

                                        <?php /* @escapeNotVerified */ echo $block->escapeHtml(

                                            $attribute->getFrontendLabel()

                                        ) ?>

                                    </label>

                                </li>

                                <?php

                            endforeach;

                            ?>

                        </ul>

                    </div>

                </div>



                <div class="admin__field admin__field-inline field-image-size" data-role="size">

                    <label class="admin__field-label">

                        <span><?= /* @escapeNotVerified */ __('Image Size') ?></span>

                    </label>

                    <div class="admin__field-value" data-message="<?= /* @escapeNotVerified */ __('{size}') ?>"></div>

                </div>



                <div class="admin__field admin__field-inline field-image-resolution" data-role="resolution">

                    <label class="admin__field-label">

                        <span><?= /* @escapeNotVerified */ __('Image Resolution') ?></span>

                    </label>

                    <div class="admin__field-value" data-message="<?= /* @escapeNotVerified */ __('{width}^{height} px') ?>"></div>

                </div>



                <div class="admin__field field-image-hide">

                    <div class="admin__field-control">

                        <div class="admin__field admin__field-option">

                            <input type="checkbox"

                                   id="hide-from-product-page"

                                   data-role="visibility-trigger"

                                   data-form-part="<?= /* @escapeNotVerified */ $formName ?>"

                                   value="1"

                                   class="admin__control-checkbox"

                                   name="<?= /* @escapeNotVerified */ $elementName ?>[<%- data.file_id %>][disabled]"

                            <% if (data.disabled == 1) { %>checked="checked"<% } %> />



                            <label for="hide-from-product-page" class="admin__field-label">

                                <?= $block->escapeHtml(

                                    __('Hide from Product Page')

                                ); ?>

                            </label>

                        </div>

                    </div>

                </div>

            </fieldset>

        </div>

    </script>

    <div id="<?= /* @noEscape */ $block->getNewVideoBlockName() ?>" style="display:none">

        <?= /* @escapeNotVerified */ $block->getFormHtml() ?>

        <div id="video-player-preview-location" class="video-player-sidebar">

            <div class="video-player-container"></div>

            <div class="video-information title">

                <label><?= $block->escapeHtml(

                        __('Title:')

                    ); ?> </label><span></span>

            </div>

            <div class="video-information uploaded">

                <label><?= $block->escapeHtml(

                        __('Uploaded:')

                    ); ?> </label><span></span>

            </div>

            <div class="video-information uploader">

                <label><?= $block->escapeHtml(

                        __('Uploader:')

                    ); ?> </label><span></span>

            </div>

            <div class="video-information duration">

                <label><?= $block->escapeHtml(

                        __('Duration:')

                    ); ?> </label><span></span>

            </div>

        </div>

    </div>



    <?= $block->getChildHtml('new-video') ?>

</div>

<script>

    jQuery('body').trigger('contentUpdated');

</script>

Now custom text field added successfully but when I close the dialog related_tire_price value gone.

Is there any additional work require or missing something?