Since I'm new here I hope I'm not the only one with this issue.
MuseScore handles Cross-Staff notes exactly the same way Sibelius does, this means, in a piano part, when you want to move a single chord note to the lower staff, MuseScore moves the whole chord instead only the note you've selected.
So, it's not possible to get this (Finale):
I'm sure there is a workaround, as in Sibelius, writing the notes in the lower stuff and lengthening the steams.
It might work as a workaround but actually it should be much better if MuseScore can handle this situation as Finale or Dorico do.