There was a time when Edit + Undo was unheard of as a concept. The closest thing we had in a world of typewriting machines was correction fluid used to paint over your mistakes. Having the ability to undo a mistake as though it never happened was a radical world-altering change. Now that we have had Edit + Undo for thirty-some years, it is easy to forget that while our digital apps have the capability, there is still no Edit + Undo in real life.
If you could add an Edit + Undo feature to one aspect of the real world, what would it look like? Where would it appear? Why?