With an older version of Audacity, while, say, I was playing tracks on Project 1, I could click the play button on Project 2. This would automatically stop Project 1 from playing, and let me continue on Project 2.
I cannot do that with version 2.4.2. I looked at settings to see if there is an option I need to choose, did not spot any.
We changed it several releases ago so that the Transport controls in Project-2 could not affect Playing (or Recording) in an active Project-1. It’s particularly egregious if an important unrepeatable recording gets interrupted in this way.