I think many of us are also aware that saving a bookmark, whether in the browser or to something like pinboard.in, is an invitation to lose it in a back hole. Whereas if it's at least theoretically in "working memory" we want to keep it as a tab. But AFAIK there isn't a really good tool--and certainly not native to a browser as far as I can tell--that lets me quickly and easily rationalize all my tabs into coherent working sets. e.g. Project X, Project Y, email/calendar/etc., to read, and so forth.