I saw a YouTube video where they created a Docker container to monitor plex and when they hit rewind, it turns on subtitles for the rewind duration. https://www.youtube.com/watch?v=YM0lVVFBZ5w. He has posted his source code on GitHub at GitHub - ThioJoe/Plex-Show-Subtitles-On-Rewind: Background process that connects to the Plex API to show subtitles temporarily when you click rewind · GitHub. Perhaps you can use his work to easily add this feature to Channels DVR.
