Short history:
There was 1 attempt to do it which ended with nothing
https://github.com/syncthing/syncthing/issues/109
https://github.com/syncthing/syncthing/pull/4331
Then there was a follow-up PR (which I was downright giddy to discover): https://github.com/syncthing/syncthing/pull/6214
That PR was just closed yesterday in favor of https://github.com/syncthing/syncthing/pull/6727 which is where the current flame of hope burns.