Assigning arbitrary shortcuts in OO.org is possible, albeit not via the GUI.

You'll note that you can save your keyboard configuration on the Customize -> Keyboard option dialog. From there you can alter the current.xml file in the zip archive it saves.

Interestingly enough, Alt+* does in fact exist as a shortcut, but it doesn't seem to work on my end. Whether this is a bug or an oversight on the developers, I can't say.

I know, inconvenient, but at least it's there. Sort of, heh.