[Nathan Shinholt]

I think I understand what you’re trying to do, but I’m not quite sure.

Lets say that Comp A has a bunch of layers in it, including Comp B. Above your timeline, you see the tab to open up the Comp B timeline. You can click that tab and drag it down to the bottom docking zone of the Comp A panel. Now you have two separate timeline windows open at once. From there, I believe you can parent specific layers or properties in Comp B to layers or properties in Comp A using the pick-whip. I hope that helps!