another alternative in Dorico 4: set Insert Scope to Global Current Bar, and just delete an individual rest or note from the first bar. That will shorten the bar by the duration deleted, and convert it into a pickup bar.
another alternative in Dorico 4: set Insert Scope to Global Current Bar, and just delete an individual rest or note from the first bar. That will shorten the bar by the duration deleted, and convert it into a pickup bar.