Slides, Ghosts, and Harmonics

See #127341: Add Glissando playback style portamento

Regarding gissando playback especially for guitar, trombone, etc., see:
https://musescore.org/en/node/183576
and:
https://musescore.org/en/node/127341#comment-719971

As for muted notes, harmonics, (and even percussive 'tapping' on the guitar soundboard) you can use a playback feature in MuseScore intended for violin.
As you are aware, in addition to bowed, a violin can play pizzicato and tremolo, so the violin's three playback channels in MuseScore can be assigned to whatever sound you want for the guitar - like harmonics, for one. All sounds are selected from the sound font (i.e.mixer). If someday you find a better soundfont which supports 'ghost note' sounds, you can use that. MuseScore's default sound font does have a 'Palm Muted Guitar' and a 'Guitar Harmonics' sound, in addition to a 'Clean Guitar' (the assigned sound when you choose 'Electric Guitar' during score creation).
See:
https://musescore.org/en/handbook/mixer
for info. about changing the playback sounds.

For mid-staff sound changes, see:
https://musescore.org/en/handbook/mixer#mid-staff-change

While the above link is about changing violin sounds (e.g. to pizzicato), you can fill the three violin channels with various guitar sounds. The trick lies in first creating a Violin score, then changing the violin sounds to guitar sounds (in the mixer). If Violin is displayed on the staff, you can change the name to Electric Guitar by right clicking on an empty part of the staff and changing the long and short instrument names in the 'Staff Properties' dialog. (See the attachment.)
(N/B. Do not use the 'Change Instrument' button. If you do you will lose the three available mixer channels - because 'Guitar' is normally set up for a single channel.)

Now, with the three channels availabe, you follow this 'how to':
https://musescore.org/en/node/50196

I have attached a sample file which uses the sound 'Clean Guitar' in place of 'Violin'; 'Palm Muted Guitar' for 'Violin-pizzicato'; and 'Guitar Harmonics' for 'Violin-tremolo'. If you look in the mixer you'll see them all.

If desired, you can use this technique to make percussive sounds - like tapping on the guitar soundboard - if you can find an appropriate sound in the mixer, or maybe find a better sound font somewhere. See:
https://musescore.org/en/handbook/soundfont#install

Still it must be said that for a score writing app, MuseScore does an adequate job of rendering playback using the basic soundfont. Plus, you can even install your own:
https://musescore.org/en/handbook/soundfont#install

For me, I use MuseScore primarily as a scorewriter so I'm content with the default sound font. On occasion I have used the 'Woodblock' sound as a makeshift guitar 'tapping' sound, but I think all these 'performance nuances' are more suited to the human performer and not so much the computer renderer.

So please open the attachment and have a listen to hear what is possible.
(BTW: I use the default sound font).

Regards.