Preroll Plus is a dynamic preroll updater and scheduler. This app bypasses the limitations Plex has for combining random and sequential prerolls (using the “,” and “;” delimiters). It works by using Plex webhooks to update the preroll string in Plex whenever a movie is started, allowing file sets that require randomization to remain randomized while maintaining a broader sequence.
For more detailed information, please see this Reddit post: https://www.reddit.com/r/PlexPrerolls/comments/1fen5vw/preroll_plus_looking_for_beta_testers/