I have a couple movies with the theatrical and directors cut. I also have movies that were split on 2 discs (LOTR) and thus are 2 separate video files.
I have combined them, however when pressing “play version” there is no known way to label them to distinguish them.
I could separate them, however it pulls the same metadata and they look indistinguishable.
Multiple versions: use the “Split” command, then edit the items’ titles in Plex to reflect the version. The file name is right there in the “Edit” window, on the “Info” tab.
If you manually split an item that’s reflecting different editions/cuts of the same movie, you can manually update the title (e.g. from Leon the Professional to Leon the Professional (Director's Cut)) and assign a poster of your choice. Sometimes, the repositories used by Plex have different posters for different cuts – however different cuts usually don’t get their own records on those databases (a few exceptions apply… e.g. there’s an own entry for the Rogue Cut of X-Men: Days of Future Past).
As per Otto’s response above… if you’re dealing with different parts of the same movie (e.g. taken from different discs as with LOTR) – you should always aim at merging them e.g. using MKVToolNix. This will give you a single file for Plex to deal with. While it’s also possible to stack the individual parts based on your file naming (e.g. including a suffix like - pt1, - pt2…), that is not supported by all clients.