Mxsmanic schrieb:

Is it possible to spot an uncoordinated turn visually, just by
watching how things move out the window, or is it only perceptible
through the movement of the aircraft?

In a sustained turn, you can't see it. But you can feel it. In a real
aircraft, that is.

I'm trying to figure out how hard I should try to keep the ball
centered.

It's goot piloting to keep the ball centered. Always work on your skills
to keep the ball even more centered. Actually, the ball is a pretty
coarse instument. So if the ball moves out of the center even by a
detectable amount, you are flying really uncoordinated.

I note that rudder can keep the turn coordinated, but changes in pitch
seem to be able to do it, too. Pulling back on the stick in a turn
not only maintains altitude, but it also seems to coordinate the turn
to some degree.

"To some degree" is not good enough. It may be good enough from a
strictly practical point of view, but it's bad style.

I've seen videos of pilots rolling an aircraft while pouring drinks.
I haven't tried that in the sim.

Shouldn't be very difficult while playing MSFS...

Stefan