When I temporarily went into teaching (5 years... lol) after a career of programming, I still wanted to write software every day. The only problem was that I only had small pieces of time -- usually 20-30 minutes here or there. It was a kind of enforced pomodoro. Of course, I suffered exactly the same problem that you do, but even worse because it would be hours before I could pick up the code again.

My solution was to try to swap out that context to disk :-) I'm back in software again and I've refined my techniques a bit. It's helpful for me because as I get older, I can hold less context in my brain than I used to be able to do anyway. There are 2 main places I store context: tests and TODOs.

I'll start with TODOs. I actually use Emacs org mode for TODOs. The best part about Org mode is that it is in a text editor. That means that I interact with it the same way that I interact with any other tool. It is also hierarchical, which means that I can embed TODOs within TODOs. Finally, it is folding, which means that I can ignore large sections of the TODO list, or move sections around with just a few keystrokes.

Basically, as I'm programming, whenever I have the thought, "Oh, I have to do this", it goes in the TODO (even if I'm just about to do it). You have to be terse because you don't want it to take more than 1 or 2 seconds to jot down. But terse is OK. I actually have 2 editors open -- one that I'm programming in and one with Org mode. I switch between windows in tmux. This is the fastest way for me, but if you use Emacs normally, then Org Capture might be faster.

Every time I finish something, I go back to org mode, mark it DONE and then reorder my TODO list. It only takes about 10 seconds to reorder the TODO list and it's useful time for me to think about what I'm doing.

The easier bit for keeping context is tests. As I'm getting near the end of the pomodoro, I make sure that I have a failing test. If everything is passing at the moment, I quickly write a failing test.

When I return from the pomodoro, the first thing I do is run the tests. This shows the failing test. At that point, I only concern myself with fixing that test. If you are used to doing TDD, then it usually only takes 30 seconds or a minute to fix the failing test. This is like a bit of a boot loader to get you back into the problem. After the test is finished, I go to the TODO and reorder them. Often it doesn't have to be reordered, but the act of thinking about priorities restores the context for me.

Currently, I'm doing some experiments where I am recording myself doing a large kata where I do one pomodoro per day (the ultimate in context killing). I don't have any conclusions yet, but the techniques I describe above seem to be working well.

I'm using Asciinema to record myself and it elides portions where you are idle for a certain number of seconds (I have it set to 2 seconds). In other words it removed bits where you are doing nothing for more than 2 seconds. By comparing the actual time spend to the length of the recording, I can see how long I was idle. At the moment, it seems to be averaging about 5 minutes for every 25 minute pomodoro. That doesn't seem to be excessive to me (since I am reading documentation and thinking occasionally).