some rework for https://github.com/opnsense/core/issues/401

src/www/head.inc

@@ -148,7 +148,7 @@ $pagetitle = gentitle( $pgtitle );
 			// hide submenu items
 			$('#mainmenu .list-group-item').click(function(){
 					$('#mainmenu .list-group-item').each(function(){
-							if ($(this).attr('aria-expanded') == 'true') {
+							if ($(this).attr('aria-expanded') == 'true' && $(this).data('parent') != '#mainmenu' ) {
 								$("#"+$(this).attr('href').substring(1,999)).collapse('hide');
 							}
 					});