[Help] How to dynamically build menu subtrees?

I'm asking for help.

# Problem description

I'm trying to figure out how menu items in subtrees could be generated at runtime to be refreshed every time menu is selected.

Currently I need to clear the menu and recreate it in the callback to an event. Is there better way?

It would be nice if menu can invoke callback automatically (like dynamic version of `with()`) to recreate the content based on the _model_ running inside the application.

Any hint welcome.

# Environment

* Operating system: **Windows**
* Backend used: **pancurses** in win32 mode
* Current locale: no such thing on Windows
* Cursive version: from git