MuseScore aligns the stems of voice 1 notes according to the rules of music theory. By contrast, voice 2 and voice 4 stems always point down; and voice 3 stems, up. Voice 1 note stems automatically flip upwards in the presence of voice 2 or 4 notes.
This action will flip any attached beam as well.
To hide the stems of individual notes:
To hide all stems in an instrument part:
Properties specific to stems and flags can be edited from the Stem tab in the Note section of the Properties panel:
Hide stem:
Stem direction: Choose Auto, Down or Up.
Flag style: Traditional (default) or straight.
Thickness: Stem width.
Length: Stem length.
Stem offset: Move the stem in a horizontal and/or vertical direction.
Stem thickness and Flag style (traditional or straight) for the whole score may be set in Format→Style→Notes.