Basically how I came around using it, was instead of having txt files, office files and a bunch of screenshots scattered around on the filesystem under the respective project directory, I started organizing such content inside Notes itself.

So you store all your documents within OneNote?

No, only those related to project delivery, that are kind of note taking stuff.

Documentation to be shared across the team is in Confluence or similar wiki platform.

Documents to be shared with the customer are in Office formats.

In systems like that, I often find myself in the frustrating situation of “I know I saw a sentence with <phrase> in it; which of the three systems should I search in? If I don’t find it, is it because the phrase was slightly different, or is there a fourth or fifth system I need to search?”

It’s maddening and is my several times per week experience.

I don't use OneNote for long standing documentation (maybe one tab is a cheat sheet). I just make a tab for each ongoing work project/client/etc, and paste stuff in there. Text from emails as a todo list which I think write comments to, notes from a zoom call, screenshots of things I need to fix, that sort of thing. I go through and edit or add comments on what needs to be done then just delete it when it's finalised and I can stop thinking about it.

It's basically a cross between a messy desk and todo list. It works well enough for me. I've tried using stuff like Trello and that is a little too much friction for me, the way you can paste text and images together in OneNote and rearrange them visually just works for me. Sometimes it just feels right to have this item "off to the side" or that sort of thing.