If not, that'd be a pretty useful addition to make this feature perfect :)

Ah snap, there is a bug where mouseover and such won't work outside of a group.
I'll push a fix for it and release.

Yep you can do that, here's an example:

#FrameSort mouseover, focus, healer
/cast [@mouseover,help][mod:shift,@focus][mod:ctrl,@healer,exists][] Spell

The #FrameSort A, B, C, etc header will take the A, B, C, etc., and place it into the occurrences of "@".

Issue fixed in release 5.2.1.

@korv114 if you update FrameSort it should be fixed now.
Thanks for notifying me about this!

I actually tried it like that but it was replacing them with @none so I assumed it wouldn't work. And didn't seem to work outside arena at least

Awesome, thanks!