Get yourself a large, high quality whiteboard. Working with it is great for visualizing things and it never gets too messy because you’re ultimately space limit

Get yourself a large, high quality whiteboard. Working with it is great for visualizing things and it never gets too messy because you’re ultimately space limited. Every now and then you go through the upkeep - this way it doesn’t ever go stale. And it’s always right in front of you. No files to open. I use a combination of the white board + Keep for more detailed stuff + per project TODO under version control.