As a feature suggestion, it would be nice if you could select custom pre-roll sequences for certain playlists, libraries, and/or collections. The thought behind this being that if you have generic pre-roll that you want to play, you could put it in the existing setting, but if a specific Playlist/Library/Collection play to have that play either an alternate or additional pre-roll.
For example, you create a generic ‘PlexRocksPreRoll’ pre-roll and set that in ‘Settings > Extras > Cinema Trailers pre-roll video’ and you also created a custom pre-rolls ‘KidsMoviesPreRoll’ and ‘ActionMoviesPreRoll’ that you could have a library called “Kids Movies” play the ‘KidsMoviesPreRoll’ instead/in addition to the ‘PlexRocksPreRoll’. At the same time, an “Action Movies” library could do the same with ‘ActionMoviesPreRoll’.