I have a composition with a ton of layers arranged in 3D space, which makes it hard to work with, and a complex camera movement. To make working easier I need to "clean up" my main comp and put all these 3D layers in a child comp and simply put the child comp into my main comp.
Now I could for example copy the camera from my main comp to the child comp so that everything works together. But since the camera movement will change a couple of times in the process and I don't want to copy every new version of the camera keyframes from my main comp to my child comp, I was wondereing if there is a way to do it with expressions.
So basically I want the camera in the child comp to do exactly what the camera in the main comp is doing, updating automatically, with expressions.
It sounds like you can click the "collapse transformations button" on your precomp and it will do what you want. That button effectively uses the current comp camera attributes within the precomp and ignores whatever camera is in the precomp. It is located on the layer properties in between the "shy" button and the quality and sampling button and looks kind of like an asterisk.