For example, PotPlayer for Windows allows users to specify multiple preferred languages in a single field, separating them with spaces. The languages on the left have higher priority. We can also use the & (AND) symbol to indicate that the subtitle name should include two words — for instance, “full” + “English” or “forced” + “English.” This is a really useful feature. In my case, it automatically selects “full” + “Ukrainian” instead of “forced” + “Ukrainian”:
Plex honors the forced flag for subtitles embedded in a MP4 or MKV container. For external subtitles, you can add “forced” to the file name (ex: Avatar (2009).eng.forced.srt).
You must also set Audio & Subtitle preferences in your Account Settings.
If the forced track matches the language preferences in account settings, Plex will prefer the forced track over a non-forced track.
Plex also remembers manual subtitle selections. If you manually select a subtitle, Plex will remember that selection the next time you play the same movie or episode.