I have a system for electronics projects where a new project gets a labeled container to store extra parts, papers, spare PCBs, weird cables I might need later...
It works pretty well, especially when I want to take a project to a meetup.
Unfortunately, I also have a bin labeled "Projects".
Same. I've got a couple of folders in my ~/Documents titled "Other".
Also, if you have projects with lots of parts, and you've got a 3D printer: have you discovered Gridfinity? (or others like Multibuild?) For the uninitiated, these are wall/drawer 42mm grids, in which you place bins that are multiples of 42. So you get perfectly-sized Tetris-like drawers and walls.