Left Alt+Enter brings up the Entry Colour dialog which corresponds to Properties for model entries; I would expect Right Alt+Enter to do the same thing, as in Windows Explorer, but it works like a normal Enter.
Funny what one can discover when editing with one hand!
The right alt key is actually an alt graphics key for getting at obscure graphics. It is a substitute for Alt+Ctrl. Beyond that, I think its use is in the gift of the programmer.
Marck (BrainStorm's programmer) might be able to either implement it as a direct equivalent to Alt in the circumstance where Enter is the accompaniment. Or he might come up with a good reason why this cannot be done.