That’s because it is not a separate movie per se. Many movie databases don’t even have this version listed.
Or they have it linked to one of the single parts. Which I am assuming is what causes it to always get matched to Part 2.
Have you already tried this file name?
Batman: The Dark Knight Returns (2013) deluxe edition {tmdb-472027}.mkv
! After renaming it, perform the complete Plex Dance with the file.
If that doesn’t help, your only other chance is to add it as an Edition of part 1, then edit the title and description accordingly by hand.
https://support.plex.tv/articles/multiple-editions/,
