I would go back to 3.6 if I could
I use Musescore to write songs - leads sheets mostly. After years of fighting with finale I found Musescore 3.6 and said Hallelujah! It was wonderful, so easy and intuitive and free!
If seems churlish to carp and complain about all the work that went into the new version but ... I would go back to 3.6 in a heart beat if I could. There is absolutely nothing I have found about 4 that is an improvement and most of the features I use, are worse. It is SO buggy. I am sure over time it will all get fixed.
Meanwhile I have either created new or revised several pieces of music in version 4 and I cannot open them with 3.6. So V4.0 it is, I sure hope the bug fixes come soon. Musescore is an outstanding piece of software and I am super grateful to the folks who put it together, I just wish the improvements really were.