For a few years, rather than really double down on some kind of electronic note taking and task management tool, I've mostly done that kind of work long hand, using pen a paper. I'm not great at using a pen to write, but it can be fun, and I quite enjoy the opportunity to take a step back, slow down, and focus on some brain work. I don't really have a system, as such, though I did read the bullet journal website and I guess I probably stole some of those ideas.
I definitely keep a pad on my desk that's some kind of loose idea of "things I want to get done today or in the next couple of days." Its less a "todo list," in the sense that it's not really an exhaustive list of everything that I need to get done, and I don't use so that I can write things down and then forget them, but more so that when I sit down at my desk, I can more quickly find something useful to do, and that every few days when look over the previous list, I can get a sense of what I've done (or not done.)
I also, and this is perhaps more interesting, have a notebook that's just for brainstorming. I've sort of intentionally selected "half-size" (e.g. 6.5" x 8.25") notebooks for this purpose. My routine is pretty simple: make a point of sitting down with a pen and a blank sheet of paper periodically and just brainstorming or writing about a topic. It's really easy to fill a page and often easy enough to fill the facing page with a bunch of ideas about whatever topic it is, usually something I'm writing but also sometimes code or another kind of project.
I think I developed this practice when writing fiction, which I don't seem to do much of, any more, (though I've been making notes for a couple of years so I suspect it'll happen,) but the idea is less to be systematic about the notes, or to collect them in ways that will be textually useful in the future, but more as a way of focusing and putting all or most of your attention on a problem for a few minutes. Often, though, the notes are useful, both because they force you to answer questions about what you're working on and can function as a creative jumpstart, both when doing work as a thing to review and also because sometimes once you start doing the mental work moving into actual work (typically for me, typing) becomes compelling. I suppose there is almost a meditative quality to the activity.
When thinking about writing fiction, the "write a half sized page full of notes" about an anecdote from a character, or a bit of worldbuilding, or a description of a plot progression (at any scale,) makes a lot of sense and use a useful exercise.
In some ways, I suppose, this is a little bit if a follow up to my Get More Done post, as one of the things I do help begin to make progress or make sure that it's easy to focus and have a clear idea of what to do when you're ready to write more formally.