If you have V2 or later, then you can have as many submenu's as you like.
Just put them between [ ] and seperate each with a ,
for example:
["One", "Two", "Three"]You can assign that to both SubMenu and SubSubMenu, but if you want to keep it compatible with the original SubMenu (yeah, major oversight from my end), then just put the first level in SubMenu and the rest in SubSubMenu, or everything in SubSubMenu.
Of course (and here is the major oversight part) you can also put everything in SubMenu. But in V1 this will cause it to give you a BSOD.