I read manual.
Didn't see answer.

Ok, is there a way to set nav screen so that it does not defaults to map every time I start the vehicle?
Wife's RX350 simply stays on the last screen she was on - usually, mpg display. I'd like to have same but, every time I switch to it and turn off the car, upon restart, it defaults back to map.
Same appears to be with ODO - I set it to trip A, restart - it defaults to overall mileage.

Any way to change that?

 

Ok, so you can't change default start up screen.
but, what you can do, is to simply press, after all that legal hala balu on the screen goes away, Home button. That brings you to a split display screen that you can customize to show what you want to see. If you go to Home>upper R hand corner there is little rectangle>highlite that and click on it> set up what you want to see on display and change layout.
That's best that can be done.