bug#57639: Toggling, in general

[Visuwesh]

[திங்கள் செப்டம்பர் 19, 2022] Richard Stallman wrote:

> Is anyone investigating the idea of a more general UI facility
> for toggling various kinds of settings?

Custom themes are a perfect candidate for this general facility.  You
can turn on major and minor modes, set variables as a part of a custom
theme.  So these "presets" could be different custom themes and we can
have a command to toggle between said themes.
[ You need not have to worry about custom file getting mangled since
  user options set by a custom theme are not saved [1].  ]

> This oculd be a prefix key.

Though, I'm lost here.  If we are talking about, say, send-mail as the
command to be run, you're saying this prefix key would change the From
address, Signature, etc. right?  Then I think having such a command
would be welcome.

> Or we might be able to do this more deeply, and implement toggling
> various kinds of settings with one Liep command.

See above, if we use custom themes, this should be trivial.

1. Only those from the special 'user' custom theme are saved.