I would like to be able to have a “Trailers” folder (like when I select folders for movies, tv shows, etc.), and have the Plex Server pull local trailers randomly from that folder, instead of having to make an extras subfolders for each movie and placing each trailer in each movie’s subfolder. This way I could add trailers from Apple or other sites for old/current/upcoming movies that I don’t own, and have them play before my movies (asi I don’t have a fast internet connection, so streaming through Plex Pass doesn’t work reliably). Or does this feature already exist?
Trailers right now are associated with items in your library. There’s no current way to have random unassociated trailers.
Hello I’m bringing this topic back from 2016.,
Currently we can configure trailers by indicating a full path to the file.
Random playback exists but only if we indicate each file. 
The idea would be to add the ability to point to a folder.
When launching a movie plex would choose a video file available in this folder to play it.
the user would only have to provide his file in trailers regularly if he wishes.
we could even do the cumulation of functions:
“A file path; path to a folder”.
By default it would only play one video file but we could consider a way to tell it how many videos to play 
