Snap To for arpeggio and glissando
Currently, it is possible to adjust the size of an arpeggio manually (doesn't work for glissando, seemingly), but I would prefer if it snapped to notes, instead.
This way, MuseScore will know how to process it, in terms of playback, layout and export.
For arpeggio, it maybe a matter of it being applied to an entire voice of notes - upon adjustment, it would spread over to others and staves.
For glissando, you would have to choose what note it will be directed to, if there's a chord.