Feature has been accidentally disabled in 2013 due to porting mistake
with inverted logic in commit 0e00aa2a85254e90ec945c8c35b6aed3389edab8:
"!parent->url().isEmpty()" became wrongly "!parent->path().isValid()"
Seems no-one missed the featzure since. Besides, the UX is questionable
custom with the separate new menus popping up instead of being in submenus.
So removing as dead code for now.