So I have a big project with several comps. I hae one comp that puts them all together in order (of which I will do my final rendering from). What Id like to know how to do is set up that "Final movie maker" in such a way that when I change the length of some of the scenes, they will auto-fit in my final movie maker comp. True, this will save me only one step, but am trying to streamline my workflow as much as possible.
That's not possible. The closest thing you can hope for is for the Sequence Layers keyframe assistant (or similar scripts) to zap the layers together, but that's it. Of course this will have to be used carefully, as these utilities mostly are agnostic of special stacking orders as required for matting etc., but if you really just generate a "render comp", it should work.