Alrighty, I can make an attempt at that. Here's an updated version of that chart I made, with numbers indicating what timelines were created first:
In "Meta In-Universe Chronological" Order (ie: in order of which timelines were created first):
[1] UNIVERSE 12 TIME TRAVELER'S ORIGINAL TIMELINE:
In Chapter 17 of the Super manga, Gowasu explains that the first instance of time travel was from someone in Universe 12. That is the first split, which creates
Cell's Timeline, at some unknown point in the past. I'm assuming well before any important events to the series would occur.
[2] CELL'S TIMELINE:
In
Cell's Timeline, the series happens, and eventually Trunks' "bad future" happens: Goku dies of a heart virus, and most of the other fighters are killed by Gero's Androids. Bulma builds a time machine, and Trunks travels to the past, creating the
Movie 7 Timeline.
[3] MOVIE 7 TIMELINE:
In the
Movie 7 Timeline, Trunks arrives and makes short work of Mecha Freeza and King Cold. He then returns to
Cell's Timeline briefly, and then returns here. They find the blueprints for a controller to shut down 17 and 18. I also like to imagine that Movie 7 occurs afterwards in this timeline, hence the name. It also helps it stand out more than "nameless/unknown timeline" does. Trunks then returns for the final time to
Cell's Timeline.
[4] CELL GAMES TIMELINE:
In
Cell's Timeline, Trunks uses the controller to shut down 17 and 18. Cell, finally having completed his development, begins searching for them. Unable to locate them and learning of their demise, he kills Trunks and uses his time machine to travel to the past, to a point farther back than Trunks had, creating a new timeline: the one where he achieves Perfection and holds the Cell Games.
[5] TRUNKS' TIMELINE:
As a result, Trunks grows much more powerful, and after the Cell Games returns home to
Cell's Timeline. This time, he defeats 17 and 18 with his own power, and later Cell when he shows up. This all causes a new timeline:
Trunks' Timeline.
[6] CURRENT MAIN TIMELINE:
Back in the
Cell Games Timeline, several things occur: the Buu arc, Battle of Gods, Revival of F, and the Universe 6 tournament. Zamasu learns of Goku's great power, and wishes to use it to punish the mortals of the multiverse. He uses the Super Dragon Balls to switch bodies with Goku and kill him, becoming Goku Black. He proceeds to seek out a less troublesome timeline in which he can enact his plan.
In
Trunks' Timeline, after he defeats Cell, Babidi comes to Earth attempting to revive Buu. With the combined efforts of Trunks and Kaioshin, this is averted, though at the expense of Kaioshin's (and thus Beerus') life. Seeing this, Goku Black selects this timeline to enact his plan to punish the mortals of the multiverse. He enlists this timeline's Zamasu, and helps him achieve immortality. They kill a very large, but ultimately unspecific, number of gods and mortals alike within this timeline's multiverse, before setting their sights on Earth. Trunks travels once again back to the
Cell Games Timeline.
There, it is eventually made known that Zamasu is behind all of this. As such, Beerus kills him. This creates the
Current Main timeline.
[7] 2 TRUNKS TIMELINE:
Goku, Vegeta, and Trunks then return to
Trunks' Timeline to battle Goku Black. He fuses with that timeline's Zamasu, and ultimately begins to threaten the entire universe (or possibly the multiverse, it's not terribly specific). Goku summons Zeno, who then wipes out that universe (or the multiverse, again not specific). Goku and co. flee to the
Current Main Timeline. Whis then suggests that Trunks go to his timeline, but at a point prior to Kaioshin dying, so as to prevent Goku Black and Zamasu from enacting their plan, at the bizarre expense of their being two of him. This creates the
2 Trunks Timeline.
