I cannot seem to get the grace notes to play back on the beat, despite that setting being selected in the playback options. Also, I’m wondering if there is an option or setting to make them play back half the length of the principal. Thanks for any help.
Only unslashed grace notes (appoggiaturas) will play back on the beat. By default Dorico creates slashed grace notes.
For note entry you can toggle between slashed and unslashed with Alt+/. The grace note icon in the left hand panel displays either slashed or unslashed.
If you have already entered grace notes you can change them to slashed or unslashed using the properties panel.