Noteplan has a great feature Synced Lines: A Synced Line is a single line of text, such as a task, quote, bullet point, etc. that is mirrored across notes. If you paste that Synced Line into another note and change the content of that line of text in any of the notes, NotePlan will sync this change to all connected copies. Check out this page for more background: Synced Lines - NotePlan Knowledge Base
This borders on discussion of ‘editable transclusions’ although this is a bit more straightforward. But I think this is still a great idea worth pursueing: use a block reference as a unique identifier and keep a line (or possibly block) synced across a vault. Most important might be the performance needed.
I’ve done some digging and think it would be possible to recreate Synced Lines in Obsidian, e.g. @TfTHacker has created a great (API) infrastructure with the Strange New Worlds plugin that possibly could be reused. In Discord user ‘boninall’ has also created something that looks a lot like Synced Lines. There’s a (currently) empty Github repository here: GitHub - Quorafind/Obsidian-Block-Reference
I’m wondering if there are any thoughts if / how this could be built or that someone already might have taken a stab at this.