Do as you are told when you are told

If you change the note of one note without changing any other lengths or adding/deleteing any ither notes to compensate, you are changing the length of the measure. If it starts off with four beats, and chsnge a quarter note to a half without compensating somewhere else, now you have five beats. Thus, you'll just end up having to delete the extra beat yourself anyhow. Not only that, but it's not accurate to say that this is only changing the one note. If you had four quarters, and you change the first to a half, the other three quarters have now changed their start time. They used to start on beats 2, 3, and 4, but now they start on 3, 4, and presumably beat 1 of the next measure. So if you thout wpyou were only chaning one note, you are wrong, you've changed all four. It's the current editing mdel that actually is closer to what you describe. The nte on beat 2 is sacrificed to make room for the new half note, but the jotes on beats 3 and 4 ate left completely upalone - just as you say you want.

Of ocourse, the problem here is that in you are probably describing what you want incorrectly. That is, you don't want MuseScore to leave the other notes where they are. You want MuseScore to move them for you, even though you never touched them. That's a fine request, and indeed, quite a few people have requested something similar (see about half a dozen other threads, mostly from former Finale users who are used to that way of working). So maybe someday, it will get implememted. But don't fool yourself as to what it is happenng. Such a mode would involve MuseScore doing considerably more than it is told - moving all subsequent notes in the measure. Whereas the current method actuallly is doing the bare minimum above and beyond what it is told - just enough to keep your measure from having the wrong number of beats, while keeping as much as possible of the rest of the measure unchanged.