I mentioned that Plex can read the NFO files that you can prepare already for XBMC by means of a special meta-agent.
However, I noticed that Plex does not read subtitles files (.SRT files) that I have also have in the folder. That was very frustrating to me. Till I saw this forum posting which solved the issue. See this link.
Go back to the metaagent that we have already updated. The XBMCNFOImporter. Add this line into the code:
accepts_from = [‘com.plexapp.agents.localmedia’]
Shut down the Synology Media Server and then restart it. Wait for a while and you should be able to go to Settings and find that you can now choose the “Local Media Assets” meta-agent which will guide Plex to use the local assets (such as subtitles etc). Make sure you selected the checkbox:
And now when you do a FORCE REFRESH of your movie library, you should see the SUBTITLES :)
Compare this with before.. where the subtitles field is not in the Metadata.
Hope this will help :)