I had this a lot in my 20s, but I notice in my 30s that an interrupt won't derail me as much.

It's not that my brain is better at caching states, I think it's to do with being a better coder: meaningful comments, better proficiency in using the IDE, knowing when to not implement something from scratch,

If you're lucky enough to be working on your own code, that can work.

Taking notes, taking notes, taking notes. Notepad as an external memory is just an amazing game changer for this. Doesn't even need to be deep, just a running tally of what you're thinking to get it to somewhere that you can reference it instead of running it on a loop in your short term memory. Makes fading in and out of it so much easier. I treat it like a conversation with myself half the time and the other half the time like I'm writing a reference book for someone else. Its worked well for fresh code, code to be, and analyzing existing code made by someone else. Cannot recommend it enough.

Note taking is great not just for recovering from distractions but also preventing them in the first place. Just jot down branching tasks that would've been a distraction and come back to them later instead of being the Hal fixing a lightbulb meme.

There's a fairly simple explanation for this. We've seen in studies that experts aren't fundamentally any better at remembering things. We just get better at chunking more and more abstract groups of information together. We can never increase the around 7 pieces of information we can hold in short-term memory. But we can increase what and how much those 7 pieces represent.