Metronome font-size input / output [MusicXML]
MuseScore doesn't preserve font-size on metronome marks when exporting to MusicXML. (I think it also doesn't do so on import.)
It does preserve font size on directions, so I think it should do so with metronome marks if they have it.
Attached is a demonstrative .mscz file, along with the musicxml that results upon export. That musicxml lacks the font-size attribute in the metronome direction, but not in the words directions.