> However some of it should be retained manually in some system - or at least I feel it should.
I question this premise. If the content you read on any given day did not the result in some change to your work product, it is really important enough to save it? Do you really need to remember all the messages, chats, articles that didn't give you any actionable answers? Or do you just keep the results that you created based on such things?
I keep none of it. I do, however, keep all my old code. Every throwaway line I've ever written is saved somewhere, even if it is just in git history on old throwaway projects. So when I do need to do something again, I don't need to re-do research or figure it out from scratch... I have my working solutions already stored.