Add support for whiteout
in my opinion MuseScore would really profit from a whiteout feature. For this we would need a concept of layers. We would need a standard layer for each type of object, as well as the control over which layer the object resides in, and an option for an object to whiteout lower objects, i.e. add some white unter the object, but above all lower layers. Optimally one should be able to specify if the whiteout should trace a contour of the object, or if it should fit the object into a white rectangle. Also an option to specify the thickness of the whiteout would be useful.
This can be really useful when doing overlapping things like putting text or dynamic into the staff (whiteout the staff lines), or putting dynamics or markings into a hairpin, or when we have inconvenient slurs. In these cases a whiteout can lead to a cleaner and more readable score.
As a demonstration I have engraved the flagship score of MuseScore 2, i.e. Reunion by Marc (https://musescore.com/marcsabatella/reunion) in Lilypond, using a bit of whiteout:
→ In bar 9 to have the Timesig whiteout the slur, thus we do not need a ridiculous high slur to avoid the collision.
→ In bar 21 the grace notes, beams and accidentals white out the ties. This is already much cleaner than the way it was before (especially on notes with ledger lines), but you can do it even cleaner using custom dash definitions, which will be a separate FR.