I might be missing something obvious here.
I am on public release channel (not beta, not forum preview), version 1.43.1.10576. But from reading announcements and support page, I think that the NFO handling would now be available to me.
I would like to test out this functionality. However, when I try to follow the instructions it doesn’t seem the functionality is there. In the Agent dropdown I only get “Plex Movie” and “Plex Personal Media” for a Movie library type and "Plex Series and “Plex Personal Media” for a TV show library type. I have refreshed (and restarted) my browser several times, but it makes no difference.
(The first thing I would want to try out is if the NFO Agent can export my current Plex custom metadata to NFO files. I also echo what others have said here before, this Agent is especially needed for “Other Videos” libraries.)