bug#15748: 24.3.50; `customize-group': Provide a way to hide/show all values

[Eli Zaretskii]

> Cc: 15748@debbugs.gnu.org
> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Tue, 10 May 2022 17:48:18 +0200
> 
> Howard Melman <hmelman@gmail.com> writes:
> 
> > When exploring new packages I often use customize-group to see what
> > settings I can change but it defaults to not showing the values and also 
> > showing only the first line of each docstring requiring me to click on 
> > "More" for every option.  Having a command to show/hide all values 
> > would be very convenient in this case.
> 
> I've now added this to Emacs 29 (as custom-toggle-hide-all-variables/`H/).

Thanks, but can we have some documentation about its usage?  For
starters, in which buffers it is supposed to be used, and how?  I
thought this was for the buffer created by customize-group, but there
it seems I can use 'H' only once: after that one time, which reveals
all the variables, any subsequent 'H' press says "Invalid widget type"
and does nothing.  (I used the buffer created for the 'display' group,
in case it matters.)

'H' does toggle in a buffer created by customize-variable, but is that
the intent?

I tried to understand whether I did something wrong by reading the doc
string of the new command, but it didn't add anything to my
understanding; it doesn't even say which "widgets" is it talking
about.

I think we need to improve the user documentation of this new feature.