How to clone or duplicate the menu?
The Advanced Menu Manager plugin will make it extremely simple for you to clone or duplicate any WordPress menu.
Simply choose the menu you want to clone or duplicate from the " Select a menu to edit" dropdown list, then click the "Duplicate Menu" button. As shown in the screenshot below.
Screenshot - 1: (Duplicate the menu)
Screenshot - 2: (Copy of menu)
You may now choose this new menu and modify its settings and name as desired.