Common ui - two stacks

Hi fellow devs,

Has anybody been able to use two activatable stacks, one for menus and submenus and one for prompts? I tried everything, googled and asked several AIs. But every time I deactivate a prompt (the prompt stack is then empty) the leafmost widget inside the menu stack is shown but the action router fails to restore the action bindings and so my action bar stays empty and no input is routed.

Or: is there another way to open a prompt like widget which should be ontop of the underlying menu widget without the menu widget to disappear?

Many thanks