I was in similar shoes as you. I even had my notes scattered all over the place, some on paper, some in different softwares. Now I use only OneNote both person

I was in similar shoes as you. I even had my notes scattered all over the place, some on paper, some in different softwares. Now I use only OneNote both personally and professionally and I cannot be happier. It has a lot of features, which helps because I can keep every idea/info/todo in one place. It has apps for everything (except Linux, but the web app works great in that case), so I can access my data anywhere. I even had a client where we all used it and we were easily able to make it work like a wiki for that project. It might seem obvious, but what really helped me with keeping my notes organized (and my browser bookmarks too, because I have a ton of those as well) is revising them periodically, in my case weekly. If you do it frequently enough, then it's really just a couple of minutes of reorganizing each time and you can keep everything nice and tidy.