Can anyone advice if  there is a mode to keep the camera of the Mavic targeted on a subject as the camera moves away and up? In other words, start at head height of a person, then pan out and up in a straight line until they are a tiny dot in their surroundings. I find it hard to keep them centered in the frame and fly in a smooth line.

It's hard to focus on a subject far away from the aircraft.
If you want a smooth line, have you tried to use the waypoint mode?

Active Track would be best for that. It will centre on the subject but you still have some control. Eventually it will lose track but it should help initially

It'd be nice if they could add Tapfly Backwards like P4P (but at your own risk). The AR Route helps you get the perfect angle, too. But I guess ActiveTrack Spotlight might help.

Isn't that what spotlight is used for?