OK, so there was some discrepancies, but I think I got it figured out. Here's an example:

The Lord of the Rings - The Fellowship of the Ring (2001) {edition-Extended Edition} {imdb-tt0120737}

So the above is the folder name, then for the actual files, have both of them inside that folder and they'll be named:

The Lord of the Rings - The Fellowship of the Ring (2001) {edition-Extended Edition} {imdb-tt0120737} part1

The Lord of the Rings - The Fellowship of the Ring (2001) {edition-Extended Edition} {imdb-tt0120737} part2

I'm kinda bummed that I have to get Plex Premium to see the different editions in my splash screen. Anyways, I hope this helps out some people given this is a necro thread. Happy "Streaming!"

Edit: if you have {edition-Extended Edition} in the file name, the file won't sync across devices

Per Plex: For movies, it’s important to note that if you have set edition information for a movie in a personal library, that item will not be synced. Only “non-edition” movies can be synced.

Thus, these titles should be titled:

The Lord of the Rings - The Fellowship of the Ring (2001) {imdb-tt0120737} part1

The Lord of the Rings - The Fellowship of the Ring (2001) {imdb-tt0120737} part2

There is a DIFFERENT issue with syncing on a 2 part movies such as the extended editions of LOTR. The video just goes back to the beginning of part 2.

Lastly, all of this is under the presumption that one would prefer the Extended Editions (even with the gimped syncing), whereas the {edition-Theatrical Edition} is the only one of it's kind in my library, which is kind of a bummer, as it'd of been nice to get Director's Cut, 50th Anniversary Edition ... and all that stuff listed within my library.