以下是链接解决方案的一个版本，可以覆盖galleryAddToolbar 有一个额外的按钮(insertTop) 要想做你想做的事情（在“functions.php”中）：

add_filter( \'media_view_strings\', function ( $strings, $post ) {
    $strings[\'addToGallery\'] = __( \'Add to end of gallery\' );
    $strings[\'addToGalleryTop\'] = __( \'Add to start of gallery\' );
    return $strings;
}, 10, 2 );

add_action( \'admin_footer\' , function () {
    ?>
    <script>
    jQuery(document).ready(function() {
        (function ($) {
            if (typeof wp.media !== \'undefined\') {
                wp.media.view.MediaFrame.Post.prototype.galleryAddToolbar = function () {
                    var media = wp.media, l10n = media.view.l10n;
                    this.toolbar.set( new media.view.Toolbar({
                        controller: this,
                        items: {
                            insert: {
                                style:    \'secondary\',
                                text:     l10n.addToGallery,
                                priority: 70,
                                requires: { selection: true },

                                /**
                                 * @fires wp.media.controller.State#reset
                                 */
                                click: function() {
                                    var controller = this.controller,
                                        state = controller.state(),
                                        edit = controller.state(\'gallery-edit\');

                                    edit.get(\'library\').add( state.get(\'selection\').models );
                                    state.trigger(\'reset\');
                                    controller.setState(\'gallery-edit\');
                                }
                            },
                            insertTop: {
                                style:    \'primary\',
                                text:     l10n.addToGalleryTop,
                                priority: 80,
                                requires: { selection: true },

                                /**
                                 * @fires wp.media.controller.State#reset
                                 */
                                click: function() {
                                    var controller = this.controller,
                                        state = controller.state(),
                                        edit = controller.state(\'gallery-edit\');

                                    edit.get(\'library\').unshift( state.get(\'selection\').models );
                                    state.trigger(\'reset\');
                                    controller.setState(\'gallery-edit\');
                                }
                            }
                        }
                    }) );
                };
            }
        })(jQuery);
    });
    </script>
    <?php
} );