The Plex Dance will do that.
But of course it is often not desirable to make the item appear as ‘newly added’ in the Plex library.
The auto-selection of forced subtitles in Plex is working very reliably in the basic situation, where a user only understands one language.
Example:
You have a MKV file with audio tracks in English and German
You also have Full subtitle tracks in English and German and Forced subtitle tracks in English and German.
I am assuming that all the tracks are properly tagged with language and ‘forced’ tags. (writing the words “english” and/or “forced” into the track title is not proper tagging!)
So if you only understand German, you go to your user profile https://app.plex.tv/desktop#!/settings/account
‘edit’ the Audio& Subtitle Settings
and set them up like this:
