Maintaining a 'mental RAM Cache' is a powerful tool to understanding the system as a whole on a deep and intuitive level, even if you can only 'render' sections at a time. The bigger it is the more you can keep track of to be able to foresee interactions between distant pieces.

It shouldn't be your only source of a plan as you'd likely wind up dropping something, but figuring out how to jiggle things around before getting it 'on paper' is something I've found helpful.