Some time I spend the whole day sitting at my computer and can't think of a solution to a problem. And some time, I'm readying myself to bed and have to note down the solution that just appear in my mind. How do you even track that? I did a time with time tracking software as a freelancer and that has been the most miserable part of my working life (and I did data entry for survey).

I'm a developer and I mostly do my thinking offline. What I do on my computer is mostly translating my idea to code and consulting docs. Also testing and communication with the team. And all of this is already fairly visible without tracking.