I agree with keeping notes for yourself. I think the key benefit is from writing the notes more than the resulting document. The act of writing it down helps you learn/remember the lessons I think. I have been keeping records of the trickiest bugs I have come across for over 15 years [1]. I believe this has helped me internalize the lessons I wanted to learn from them, so I (mostly) won't repeat them.

Also, when you leave the company you keep your own notes.

[1] https://henrikwarne.com/2016/06/16/18-lessons-from-13-years-...