GH,
Be advised; in RB those undo functions are only available during a session. Once RB is closed it will wipe those temp files it had stashed for Undo.

In other words, if you close RB, you can't open it and undo anymore .. RB cleans up behind itself when it closes.
These snippets are kept in your Audio Temp Directory which is defined in Audio Prefs.

Back on Topic; I don't think the new version ships with those older realtracks, so I don't think they are needed at all, but you may have used them in a previous project.

I do not work here, but the benefits are still awesome
Make your sound your own!