The real world solves it too btw. in the same way a relational database did: Indexes ;) Tagging is nothing but different indexes of the same underlying thing. Be it a book or an email or whatever else.
And this top level comment is actually weird to me. Maybe I'm just a non-Chrome-user? I use Firefox. I never bookmark anything any longer. I literally just know what to type to get to what I need to from the history. Like HN. I literally just type n into a new tab and HN is the first suggestion based on how often/recently I went here. No manual bookmarking or anything non-local needed.
Similarly at work I just know how to find certain things by typing into the search bar. And it even learns from recency. Our app URLs recently changed and I had to start typing the new unique parts of the URL recently for a few tries until it went up in the recency bias calculation. Sure like I had to scroll down a few entries in the history search a few times. Now I just know what to type to get where I want to again.
I see others struggle with rigid bookmark structures that they can't find anything in like ever on the regular though (URL change or not) :( And (at least with firefox) those bookmarks would even get searched too! Of course, unlike history they would have to manually update bookmarks. I really don't get it how people even still use bookmarks any longer.