What triggers a sync besides the timer?

A sync happens when: the app first opens; the repeating timer fires (Auto only, within your Active hours); you press "Sync now"; a push runs (a push always syncs first); and shortly after the app writes a change (it re-checks about 0.6 seconds later to confirm the change settled). Bringing the window to the front or waking your Mac deliberately doesn't trigger one — sync sticks to your schedule.