OneNote is nice and sweet on the surface, but a p.i.t.a. to maintain when it grows. Notebooks are tied-in to your OneDrive in an awkward way, the book structures are very easy to scale up but very tedious to scale down, and you get encouraged to write long pages with different content types, but that makes the entire thing difficult to sort through when you need something specific. I recommend Sticky Notes instead. It's like OneNote, but with notes instead of pages, and a heavy emphasis on "let's search through the pile when you need something specific, don't worry about structure". Overall, it scales better because it has less parts to maintain.