Score Tabs
Don't think this is a bug, but whenever I open a score, even with musescore4's dialogue box, it opens a new window of musescore4 just for that score. I really liked being able to switch between my different scores in the same window in musescore3.
Comments
MS4 no longer has that feature
See discussion in the Issue Tracker:
#338910: Tabs behaviour change - Opening two scores on the same window