I have no specific technique to manage all of good contents on HN. If I find a post or thread that has a good content, I usually upvote or favorite it. But, as you said before, it will grow bigger and bigger as a list on your "upvoted submission" section profile.

I think using Pocket or other bookmarking tool is one of the method because you can give a tag or keyword to your bookmarked content (searchable).

Well, at the end, I agree with someone who said you don't need know everything. Our brains have a limit. Choose the topic that suits with you.