implement metric modulations in metronome marks

Again for braille translation and easy engraving, especially for blind to input special metronome marks. See discussion here for the original question and example:
https://musescore.org/en/comment/1061272
This is a swing metric relationship, and the current solution in Musescore is quite inaccessible and complicated. Finale and Sibelius can both do it easily, while Finale can import and show the Musicxml attached there correctly. It's a standard way to do this in Musicxml, so I think Musescore should also do it in standard way, exporting as standard Musicxml. In the Musicxml 3.1 Schema, it says:
"The metronome type represents metronome marks and other metric relationships. The beat-unit group and per-minute element specify regular metronome marks. The metronome-note and metronome-relation elements allow for the specification of metric modulations and other metric relationships, such as swing tempo marks where two eighths are equated to a quarter note / eighth note triplet. Tied notes can be represented in both types of metronome marks by using the beat-unit-tied and metronome-tied elements. The parentheses attribute indicates whether or not to put the metronome mark in parentheses; its value is no if not specified."
So both noteheads, ties and tuplets should be implemented in the metronome mark section. The beaming should also be automatic if smaller notes are used. Probably a bigger feature request.