It seems that arpeggio can only be added to a single chord. I tried highlighting several chords (over several measures) and add arpeggio (both the keyboard way and the mouse way), only the first chord gets the arpeggio, the rest of the chords are unchanged. When I checked the ‘Dorico Help’, I found this statement: “You can only add one arpeggio sign to one note or chord at a time.”
I hope the future update will allow adding arpeggio to multiple chords. This will save a lot of time when entering arpeggios for piano score.
You can use the Alt (option) key to copy the arpeggio mark quickly; it will adjust its height automatically. That’s still not as fast as what you’re asking for, but it’s quicker than using the right-hand toolbox for every chord.
Just found this because I was in the same situation: selected a load of chords and tried to put arpeggios on all of them at once. Please consider implementing this possibility in an update.
If the arpeggios appear at the same resolution / harmonic beat: Enter a couple of bars with arps manually and press J > filter arpeggios and hit “R” (repeat).