The way Xenoverse works leads me to believe that as long as timelines differ only slightly, time just fixes itself and timelines merge. That being said, we know of a few indisputable alternate timelines which differed so much that no merging is possible.
- - "Main" Timeline
- "Original" Timeline (now called the Alternate one)
- "Movie" Timeline
- "GT" Timeline
We start with Main Timeline Trunks. This is the one that grew to be kinda spoiled and cocky and the last we know about him is that he participated in the 28th Tenkaichi Budokai.
From here, we know that there are manga, anime and "Kai" variations, but those are all closely related so they may just merge with each other.
From this one, we have the Movie Timeline Trunks, as we know, movies differ very much from the main timeline but they are also mostly interconnected so logically they should all fall under the same timeline. This one is the one that fights Broli, Bio-Broli, a whole army of the undead and Hirudegarn, gaining a sword from Tapion.
Now here's where it gets tricky. GT Timeline Trunks supposedly follows the anime timeline, but there are a few minor inconsistencies, including the fact that this Trunks owns a sword. Also, his hair seems to be a deep purple. This timeline may actually be the same as the Movie Timeline, it honestly wouldn't really alter anything, as far as I know. Maybe they are actually a unified Toei Timeline.
So here we have at the very least "main" Trunks and Capsule Corp President Trunks.
Now we tackle Alternate Timeline Trunks, and oh boy...
The one we always think of is the one that became the last remaining Saiyan. But the original one, from the original unaltered timeline is the one Cell killed.
Now applying goofs and mistakes, we have the one from manga chapter 335 who said he fought #19 and #20. Applying the Xeno rule of "every timeline is possible", we can assume that this one is a valid one too and differs from the one we later see coming back from the future. Although this one may actually be the one Cell killed from the unaltered timeline.
Another mistake is the difference between the anime and the TV special versions of the future. In DBZ episode 164 we see a Trunks who fought for longer alongside Gohan, this Gohan seems to have lasted a few more years because Trunks already had his sword. Although since this, the TV special and the manga only differ slightly, all these timelines may have been merged.
We do however have a Trunks who appeared in the movies and fought Merged #13, Broli, Hatchiyack and Bojack, this one has to be different, he may hail from one of the previous mentioned timelines. This one may be the same from Another Road... but that's a whole mess of a story in my opinion. May one day I'll cover it.
But during Super, the alternate timeline gets erased but Whis goes back and warns Beerus before he is killed by Zamasu, thus creating yet another alternate timeline where two Trunks co-exist.
For alternates we have at least the Trunks who was killed, Survivor Trunks, Another Road Trunks and... Yet Another Trunks?
And thus we reach the Xeno times. This is even better!
So now we have at least 3 versions of this. Originally there was Dragon Ball Online. In this timeline everything but the manga is ignored, so we already know this one isn't any of the previous mentioned Trunks'. Then we have Xenoverse Trunks and Heroes Trunks. All these three are Time Patrollers, but the last 2 have fought different enemies. Xenoverse Trunks fought Demigra and later Final Form Mira. Heroes can transform into Super Saiyan 3 and has fought the Dark Empire. Although these last two may be Another Road Trunks and Yet Another Trunks. Unless they are actually all the same but from different points in his history.
Anyone I forgot? Let me know.