Created new sub-menu item - not appearing in tree

Using Revo 2.0.5 on two different sites.

I’ve added a namespace
Added an action to that namespace
Added menu action to Components
- all fine
Now I’ve added sub-menu action to my menu action (using same action as menu, but with different lexicon entry and handler)

Result - after clear cache and reload it appears in the top menu buttons, BUT it doesn’t show in the Menu tree controller. I can see the action in modx_menus, with a parent in modx_actions, and the action works fine.

Is this non-appearance in the tree control because (a) I’m setting it up incorrectly, (b) it’s not supposed to have submenus or (c) a bug?