I don’t know if this is the right place to post this but, in the absence of built-in functionality for wishlist recordings in Plex (to schedule a movie to record which isn’t currently in the EPG), here is a Python script I have created which automatically schedules recordings of movies in your Watchlist when they appear in the EPG (and aren’t already in your library).
You just need to update the IP address and token in the script and schedule it to run.
You can then add a movie to your watchlist from Discover and, when it next appears in the DVR, when the script runs it will schedule it to record.
This currently only works for movies, I’m not sure if I’ll be able to get it working for TV shows as the scheduling options are more complex (e.g. new episodes only or repeats, etc.)