Support for "Hanging" ties used in percussion scores.
As someone who uses MuseScore primarily to write for percussion, one of the most glaring feature omissions was hanging ties. They're common in percussion scores to indicate that the instrument should ring out, rather than be choked. In drumline they're commonly used to differentiate between open cymbal crashes and choked crashes.
In the first screenshot you can see how they are meant to be rendered. The tie isn't connected to anything, but rather hangs freely from the note. The second screenshot, taken from MuseScore, is a mess. Trying to manually adjust every tie is arduous, and changing anything within the score will instantly mess all of them up again. Simply adding a "ring" or "hanging tie" feature that automatically formats them the correct way would be a true lifesaver for making professional-looking percussion parts.