How you defend someone as a screener should override what you want to do to someone as a ballhandler. How do you want to defend the ballhandler -> how do you want to guard Player A as a screener Other than changing the setting every time the CPU Mavs change their lineup, there is no way of adjusting. But obviously if Dirk is the screener you want to stay attached. I'm happy leaving Powell out there and focusing both my defender and the screen defender playing for Barea. This is a bit of a problem as sometimes they will play Dirk at the 4 and non-shooters like Dwight Powell at the 4. So with JJ Barea I can choose how to play screens with him as ball handler regardless of who sets the screen. How I defend the screens is based entirely on the ball handler.
If Im the Bucks, I go through the Mavs player list. Right now we apply the individual defensive settings based on the ball handler, rather than the screener.