If you mouse over an enemy on the field, that highlights the enemy portrait in the turn order.
I am amazed that still after all this time, it STILL does not work the other way around: highlighting an enemy portrait in the turn order does not highlight the associated enemy on the field. You have to mouse over enemies to find out where they are in the turn order. It's a trifling annoyance, but a baffling one in a game designed around tactical termination of targets.