You can assign them directly to the Character, but then they don't show up on the rest of the team, so... technically, no, I don't think there is a way to do it that way at the moment. I was also trying to think up a way to do this for my Menus (specifically the Heroism one that you saw, as well as, the others), but I think I'm just going to create 5 different Menus and have them all placed where they would be placed if the Shaman (or whatever character) was in a certain spot of the party.

So, the Menus would be labeled Shaman01, Shaman02, Shaman03, et cetera... and if the Shaman was in the third spot in the party, then I'd drag and drop Shaman03 onto my Character Set, export, and the buttons would then be positioned correctly. It might sound a little tedious, but if I'm already changing out my characters in my team it only takes less than a minute to drag and drop some new Menus onto the Character Set as well before I export.

This might sound a bit confusing, but now that I'm talking about it I might go ahead and include it in my new "UI update" video whenever I bring back the MWM series (soon™).