The same thinking everyone claims is happening subconsciously when they're showering or riding their bicycle or whatever that doesn't focus on their code also happens to me when I'm not focused on that code.

Recently I had to decide how to rebuild a fairly large component of our compiler (several passes, artifact emission, etc). It took me about a week for the idea (for how to best do it) to occur to me. I spent that time working on our runtime instead. Then once I had the design/architecture, I worked for 2 weeks straight to implement. And during that 2 weeks I figured out a path forward on something I was blocked on in the runtime.