wp-multisite-waas/views/base/edit/widget-save.php

<?php
/**
 * Save widget view.
 *
 * @since 2.0.0
 */
?>
<?php if (!empty($labels['save_description'])) : ?>

  <p class="wu-mb-5">
    <?php echo $labels['save_description']; ?>
  </p>

<?php endif; ?>

<div class="wu-bg-gray-200 wu-p-4 wu--m-3 wu--mt-2 wu-border-t wu-border-l-0 wu-border-r-0 wu-border-b-0 wu-border-gray-400 wu-border-solid">

  <button type="submit" name="action" value="save" class="button button-primary wu-w-full">
    <?php echo $labels['save_button_label']; ?>
  </button>

</div>