Thank you for your answer. I understand by your reply that somehow it is not available in Dorico 2, somehow it has disappeared.
I just tried in Dorico 1.2.10 and it is great the way it works. One could start playback while looking at the full score and then switch to any part while keep on listening the full score. And also, one could start playback in any of the parts and listen only that part, even while changing to the full score or any of the other parts.
I always thought that it was a very flexible way to audition combination of the written music --being able to listen any part or the full score and view any part or the full score.
I am glad that as you said, “… no doubt return to in a future version.” I hope it will come back in Dorico 3.
Best regards and thank you for making the best notation program ever!