Just spent a few minutes on this and I agree. It doesn't appear to be possible, and as you mentioned, it's pretty simple to edit a voice, save it, and assign to the right hand. What is missing is the ability to edit the style to use a "user" voice vs. the various factory sounds. Although I don't think I have a need (at least I don't think so), disappointed to see that the user banks are not available in this case.