Haven't been able to find a tutorial on this, but can I cut the screen in half, and then change the timeline of one half? What's the best way to do that?
I'm not really sure what you're asking to do here so I'll take my best guess. you're trying to do a split screen of the same composition on both halves of the screen, but you'd like to make changes to one half and have those changes only affect that half? Does that sound about right?
If that's the case, then your best bet would be to just duplicate your composition, then drag them both into a new composition and split screen them. That way you can change things in each independently. The only problem is that if you would like to make the same changes to both, then you have to do the same for each one.