RE: Infrastructural complexity.

[Drew Adams]

> > Basically,
> > a narrow area for listing a thin menu of commands but with a
> > "tree structure" so you can dig down to sub-commands or pop
> > back up to parent menus.   With a "home" or "clear" command for
> > getting back to the root of the command tree.
> 
> That sounds very similar to M-x tmm-menubar. It seems to lack a
> feature to back up though.

I think you're right, but LaCarte does let you back up.

LaCarte uses normal Emacs completion. Just remove text from the right to back
up, just as you do when navigating the file hierarchy using file-name
completion.

LaCarte could be added to Emacs, as a replacement or as an alternative to tmm.
Or similar code could be written for Emacs from scratch. The point is that
completion is a handy way to explore a hierarchy (down, up, sideways).

http://www.emacswiki.org/emacs/LaCarte

(You do not need Icicles to use LaCarte. The page mentions Icicles because
completion that is not just prefix completion enhances how you can navigate the
menu tree/forest.)