Can the MuseScore playback system do artificial harmonics (for strings)?

All playback is based upon the soundfonts you have installed. If your soundfont supports the sound then MuseScore does. There is no harmonics sound in the GM standard so no harmonics sound in MuseScore. You can search for a soundfont that supports this and then you can play it.

I normally notate the harmonic and mark the notes not to play. I then enter the note I want to hear in another voice and make it invisible. You don't get the same quality as you get from an harmonic, but you get the right pitch.

As Mike 320 says, there will be a sound, but it will not be the velvety harmonic sound you would desire. I see you are new, so let me assume you are not familiar with the software:
(from Mike 320)
notate fundamental tone in voice 1
notate harmonic above in voice 3 (better use 3 for stem direction)

delete play in fundamental
delete play in harmonic
make invisible all unnecessary stems, etc
make sounding note invisible ( the usual preference)

the noteheads for harmonics can be found in inspector. (head group and head type)