Hello Cadenza!
As far as I can see Dorico treats artificial harmonics like natural harmonics. They both use the same "Playback Technique" "Natural harmonic 1". In the expression map there is an entry for artificial harmonics to sound an octave lower to compensate the octave shift in the preset, but unfortunately this "Playback Technique" does not get assigned to artificial harmonics. Natural harmonics are played correctly, so adding an entry for natural harmonics to sound an octave lower, would make the natural harmonics sound in the wrong octave. If you are only using artificial harmonics in your score, you could edit the expression map and transpose the Natural harmonic entries down by 12 half-tones.
Best regards,
Andi
Vienna Symphonic Library