newsupernova/vendor/magento/module-backend/view/adminhtml/templates/system/design/edit.phtml

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
?>
<form action="<?= /* @escapeNotVerified */ $block->getSaveUrl() ?>" method="post" id="design-edit-form">
    <?= $block->getBlockHtml('formkey') ?>
</form>
<script>
require([
    "jquery",
    "mage/mage"
], function($){

    $('#design-edit-form').mage('form').mage('validation');

});
</script>