Integrate palm mute playback with palm mute lines
MuseScore at its current state does not provide a playback feature for palm muted notes (guitar, bass). This playback effect can be achieved by reducing the playback duration of the muted notes to half or one quarter of the overall duration of the note; similar to staccato notes.
I have attached a file demonstrating the desired playback effect by using hidden staccato note markings as a workaround.
A similar playback solution has been used in other MIDI based notation/tablature software, such as Guitar Pro and TuxGuitar.