MuseScore aligns the stems of voice 1 notes according to the conventions of music theory. By contrast, voice 2 and voice 4 stems point downwards by default, while voice 3 stems point upwards. Voice 1 stems automatically flip upwards in the presence of voice 2 or 4 notes.
Select either the notehead, stem or attached beam (if any)
Use any of the following methods:
Press X
Click on the "Flip direction" icon in the Note input toolbar
Select a stem direction from the Stem tab in the Properties panel
This action will flip any attached beam as well.
Select the stem
Use one of the following methods:
Press ↑/↓ to extend or shorten the stem
Change Length in the Properties panel
To hide the stems of individual notes:
Select one or more noteheads
Go to the Properties panel
Select the Stem tab
Select the checkbox next to Stemless
To hide all stems in an instrument part:
Right-click on the staff and select Staff/Part properties
Click on Advanced style properties
Select the checkbox next to Stemless
Properties specific to stems and flags can be edited from the Stem tab in the Note section of the Properties panel:
Stemless removes the stem (and associated beams) from the selected note(s)
Stem direction:
Auto determines the direction of the stem according to the voice of the selected note(s)
Up and Down override the default stem direction
Flag style sets the appearance of flags for the entire score to either traditional (default) or straight
Thickness determines the stem's width
Length determines the stem's length
Stem offset can be used to move the stem in a horizontal and/or vertical direction
Global settings for Stem thickness and Flag style may also be set in Format→Style→Notes.