Add a simple standard way of toggling between normal level and maximum level?

[phil-s]

The 'level' functionality via C-x l is handy for setting a default, but the UI feels cumbersome whenever I want to check whether a feature exists on some currently-hidden level. As far as I know, to use an option which is not at my current level I need to use C-x l and then either change the overall level, or change the level of the specific option, and then quit back to the regular menu, and finally do the thing. And if I don't want that option as a default, I then need to go through the same process to undo it afterwards.

What I'd like is a standard key binding to temporarily enable the maximum level so that I will immediately be able to see and use any available option. That would let me keep the default level set to cover my day-to-day options, and still give me easy access to everything else.

Alternatively, much like M-1 .. M-4 are bound to the section visibility commands in Magit, maybe M-1 .. M-7 could be bound to "change to level N" in transient menus? Or even simply 1 .. 7?

[tarsius]

I've implemented this (the boolean toggle) in 9257245. It's available on C-x a.