Wolf Munroe ☎I'm a dork.
I like #mpv. That's not why I'm a dork, but...
I just compared instances of mpv.conf in my home directory. I checked where each one stored watch_later data. For all the ones that were identical settings, I made them hard links with an extended attribute specifying the watch_later data location.
I know they could have been symlinks, I just think hard links are neat because each one "contains" the data. Also extended attributes!