Yeah, it's that elusive "fourth timeline" that was dropped. My belief is that it was the second timeline actually created, when Trunks went into the past for the very first time. In other words, the timelines in order of creation are...Kamiccolo9 wrote:Funnily enough, the Chozenshuu timeline doesn't list one of the timelines present in the Daizenshuu excerpt that timeline came from.
There is another timeline I've seen floating around that includes a few movies, along with a disclaimer saying that they wouldn't actually fit where they are placed. I don't know what it's from, but I've seen Herms reference it recently.
Timeline 1 - "Cell Timeline"; Trunks was killed by Cell at the end of this timeline because he didn't know he existed.
Timeline 2 - "??? Timeline"; The Trunks who was killed by Cell came to this timeline, and the deviation point from the "main" timeline is that Trunks doesn't come back a third time, because he's died, so the artificial humans are defeated (either in battle after the warriors trained in the Room of Spirit and Time) or by deactivation. Cell likely doesn't show up unless it's at the end of the timeline, at which point, he'd probably be easy pickings for the Super Saiyajin, regardless of what level they reach (that is, if they aren't killed by Bū, provided there's even enough energy to reawaken him).
Timeline 3 - "Trunks Timeline"; Trunks goes back in time to the timeline we all know and love.
Timeline 4 - "Main Timeline"; 'Nuff said.
The best explanation I can give for why the "??? Timeline" was dropped was because we knew practically nothing about it, so it was easy to write it out of existence. For an in-universe explanation, I'd just say that it was overwritten when "Trunks Timeline" Trunks came back in time, effectively replacing the "??? Timeline" with the "Main Timeline". Those are just my thoughts, anyway.
I think I know which timeline you're talking about; if it's the one I'm thinking of, it just mentions where two or three of the movies theoretically would take place. (I feel like it was Movie 5 and Movie 12, but don't quote me on that.)