function plt_hide_multiple_domain_mapping_on_single_site_menus() {
//Hide the "Tools → Multidomain" menu.
remove_submenu_page('tools.php', 'multiple-domain-mapping-on-single-site/multidomainmapping.php');
}
add_action('admin_menu', 'plt_hide_multiple_domain_mapping_on_single_site_menus', 11);