WP Custom Nav Menu Meta Box

<?php
//Add custom nav menu meta box
function mynav_add_custom_box() {
    add_meta_box(
        'add-mynav',
        'My Menu Choices',
        'mynav_show_custom_box',
        'nav-menus',
        'side',
        'default');
}
add_action( 'admin_init', 'mynav_add_custom_box' );

//display nav menu meta box, copy of wp_nav_menu_item_link_meta_box()
function mynav_show_custom_box() {
    global $_nav_menu_placeholder, $nav_menu_selected_id;

    $_nav_menu_placeholder = 0 > $_nav_menu_placeholder ? $_nav_menu_placeholder - 1 : -1;

    ?>
    <div class="customlinkdiv" id="customlinkdiv">
        <input type="hidden" value="custom" name="menu-item[<?php echo $_nav_menu_placeholder; ?>][menu-item-type]" />
        <p id="menu-item-url-wrap">
            <label class="howto" for="custom-menu-item-url">
                <span><?php _e('URL'); ?></span>
                <input id="custom-menu-item-url" name="menu-item[<?php echo $_nav_menu_placeholder; ?>][menu-item-url]" type="text" class="code menu-item-textbox" value="http://" />
            </label>
        </p>

        <p id="menu-item-name-wrap">
            <label class="howto" for="custom-menu-item-name">
                <span><?php _e( 'Link Text' ); ?></span>
                <input id="custom-menu-item-name" name="menu-item[<?php echo $_nav_menu_placeholder; ?>][menu-item-title]" type="text" class="regular-text menu-item-textbox input-with-default-title" title="<?php esc_attr_e('Menu Item'); ?>" />
            </label>
        </p>

        <p class="button-controls">
            <span class="add-to-menu">
                <input type="submit"<?php wp_nav_menu_disabled_check( $nav_menu_selected_id ); ?> class="button-secondary submit-add-to-menu right" value="<?php esc_attr_e('Add to Menu'); ?>" name="add-custom-menu-item" id="submit-customlinkdiv" />
                <span class="spinner"></span>
            </span>
        </p>

    </div><!-- /.customlinkdiv -->
    <?php
}