New character nomination of Emony Dax in Star Trek AOS - technically she was a character introduced in Star Trek: Deep Space Nine, however wider Trek canon (novels) includes her having contact with Leonard McCoy when he was in medical school, something which is not super likely to have been derailed by the events at the beginning of the first AOS movie.

I leave it up to you where you want to draw the line on whether that's acceptable - if it's helpful to your decision making, I see her as a potential element for worldbuilding the ways in which AOS does/doesn't diverge from TOS.