Menu manager!. With this plugin admin can create menu with menu url, text, priority and much more options are there. Using this plugin admin can also say that which menu is visible to whom (i.e logged in user, public or admin only) . Here you can set menu item for Topbar and Sitemenu . you can do that by selecting menu type as either topbar or sitemenu. Admin can also set priority of that menu option which will help to position the menu item. Admin can also create a child menu or submenu of menu. so that is visible under the parent of selected menu. you just need to select your parent menu and then hit the button with label 'Add Sub'. after that you just need to fill the details as same as in parent case. and if you dont want that menu option just click the 'X' button to delete the menu-option.