Piano Note Display During Playback
In Musescore 3, the piano view would display the notes that occurred during playback in addition to displaying selected notes. In Musescore 4, only selected notes are displayed. It was a marginally useful feature, but I've found myself missing it. It was helpful for me when making vocal arrangements to check at a glance. Although, part of why I miss it is that it was just fun to look at.