From support.plex.tv/hc/en-us/articles/200381043-Multi-Version-Movies
"Note: This feature is not intended for situations where you might have, for instance, both a “theatrical” and “director’s cut” version of a movie. Likewise, it is not appropriate for 2D vs 3D versions. Those situations are best handled by Splitting the movie into separate Library items.
This is one thing that really, REALLY bothers my organizational OCD. 
When I’m browsing through my library on devices, or even the web app, I hate seeing (or having to make) multiple items for each variant of a movie (i.e. Theatrical, Directors Cut, etc.) cluttering things up, when it would be so nice, clean, and easy to merge them into the same group (like you can for the various resolutions) and then when wanting to watch a variant, just select it from a button, drop-down menu, or similar.
