help should be context dependent

[jillr]

It's not clear to me from :help which options are available to me in what parts of the tui.

For example I tried to :w foo_file from the :collections menu (just to see what it what do) and afaict nothing happened (nothing in the log with debug enabled).

I want to be able to :filter (or really, regex search) in a doc (I understand I can't) but checking help while in a doc doesn't give me any indication this option is unavailable here.