Mega menu : can't display module in megamenu

I have a small problem. i have a menu where i want to put a module in the submenu.
My menu organisation is the following :

Main item
L_ _ Submenu (separator)
L_ _ Item 1
L_ _ Item 2
L_ _ Item 3
L_ _ Item 4
L_ _ Submenu (separator)
L_ _ Module here
L_ _ Submenu (separator)
L_ _ Module here

I just can add a module where i want. I send a screenshot if you can solve it.
Thanks !