Writing guitar arpeggios by hand is slow and unproductive. To my knowledge, the only way to do it at the moment is to manually enter notes, assign strings etc. Midi guitar input also doesn’t work for this task, as string information is either non-existent or lost between the guitar and Dorico.
Dorico already has an extensive guitar chords diagram library, which is half way there to the chords realization. In essence, the diagram IS a kind or realisation, but currently it’s not translated to notes.
Dorico could have a few options to realize the chord diagrams. The simplest option would be to add all chord strings as notes in place of slashes. Advanced option would be to create arpeggios from (not yet implemented) arpeggio patterns.
Alternatively, Dorico could offer a way to realize chord diagram by entering string numbers. E.g., if the chord is Fm7, keyboard entry would trigger the strings (there could be a computer keyboard mapping which kinda approximates guitar string position, e.g. space:6, M:5, K:4, O:3, 0:2:-:1).
Alternative option would be to use chord diagrams and midi (guitar) input to create notes. Eg, if Fm7 chord is in the chord diagram, put those notes in the score/tab when they are played.