Here’s a trivial implementation of this feature:
I’ve been looking for an alternative to VoodooPad recently and Obsidian seems promising, but the lack of this feature has been a big no-go, so I made one myself. I hacked this together in two days, so it’s rough, but it works.
This only updates the document you’re currently viewing as maintaining a state over all files in the vault was a performance nightmare. With ~10,000 files in the vault, parsing a long open file for mentions of all of them takes about 150ms. Not great, but I can live with it for now.
Maybe I can improve on this in the future after I learn bit more about how Obsidian’s internals work.