Re: C-h w undo RET says "undo". Where is it?

[Yuri Khan]

On Fri, 23 Jul 2021 at 12:11, Marcin Borkowski <mbork@mbork.pl> wrote:

> Emacs tells me that `undo' is bound to several keys.  Personally, I use
> C-/ almost exlusively, but C-h w undo RET says that it's also bound to
> <undo>.  Where is that key?  More precisely, can anyone show me an
> example of a keyboard (preferably a modern one, not a historical
> curiosity) possessing such a key?

[Legend has it][DT] that Undo was a key on early keyboards, starting
with Xerox Star, later Xerox Docutech, Sun Type 4/5/6/7.

[DT]: https://deskthority.net/wiki/Fun_cluster

Modern mass-produced keyboards do not have an Undo key.

If you are building a custom keyboard based on TMK or [QMK] firmware,
you can turn any key into Undo by assigning the KC_UNDO key code to
it. Be aware that some modern software will ignore it even if they do
have a notion of undo and handle Ctrl+Z.

[QMK]: https://docs.qmk.fm/#/keycodes