Many thanks for the reply. That really helps!
While I was thinking about this and using a tablet (do not often do this), I had another tought. Would it be possible to totally disable the top menu links and just have them open and close the sub-menus? Then I would copy the top level link with jQuery to the top position into the sub-menu and call it “Overview” and maybe even highlight it a bit with CSS.
I felt this the least confusing option for users on touch devices. The top-level items always just toggle. Not sure how to differentiate it towards desktop usage of the menu though…