Spawning my own widgets is not a problem.
I was using “Menu Anchor” element - it is specifically designed to spawn a widget of a given class when triggered (it has some options to make it easier to specify a relative location of the new widget). So I don’t create a widget by hand - I call “Open” on the Menu Anchor and it spawns its “menu class” widget. There is however no way that I can see to access that new widget.