[Mikhail_Edoshin]

It works. There's even a psychotherapy method called "problem-solving therapy"; all it does is that it formalizes the process of finding a solution to a problem: define the problem (what you have and what you want to have), outline possible approaches, evaluate, choose. I myself use something like that in my work (software development) with a text file and I can attest that following the steps often helps me to find or choose a different solution than what initially popped up in my head.

It doesn't solve all problems, e.g. a complex problem that is hard to understand are not a good fit; if I notice that what I write is lengthy or that I keep returning and restating it, then this is that kind of problem; here I normally leave the desk and try to sketch it on paper.

Very seldom I look through the file to find why I've made a particular choice; I don't think logbooks are of any use here, it's better to document the design elsewhere, closer to the product. I'd say logbooks are write-only (although they may be a source for the docs).