New Menu Module not Display in the Child menu - WebDesigner - 1IM

Hello,

I'm trying to add a new menu module in the Child Menu I've created in a custom ROOT_Menu (my goal is to get the following) using Web Designer:

ROOT_MENU

 > Child_Menu
                     > New menu

 

Is this possible to do this? it's like a 3rd level menu

I've used the same process like when you add a new menu in the root menu, also I tried putting the identifier of parent menu item (Child menu) in the New menu to force it, but didn't work 

Any ideas? Thanks