Yep, I caught that mistake in the 1.02 version available now:

[Link: ampersand.hypermart.net]

Clearing out a key is included in the manual: [Link: hudsonag.com]

I assume you would clear a shifted key the same way you clear a regular key but with the MAGIC key thrown in. (Just like defining the key). In fact, it seems that clearing out anything is just doing whatever command you did to set it in the first place and jelecting that item twice.