Since making Bear actually use YAML for organizational purposes basically requires writing an entirely new organizational system, I had a thought today about another way to do it.
Import and export mapping.
For instance, on importing you could have Bear pull the title: key and make it a title on the post, make the date: key the note creation date, and, say, anything in a tags or categories key into tags. Maybe even, if someone has custom keys, they can map them to custom tags.
Bear then either ditches the YAML from the note altogether or leaves it.
For exporting you’d do the reverse: map the note title to a title: key, creation date to date: key etc.
Obviously this still would be work for Bear developers but presumably noticeably less so than an entire YAML organizational engine.