I like some of the bookmarking ideas you highlighted. Both and Chrome and Firefox bookmarks seem completely neglected.

Interestingly, Microsoft’s Edge browser have a feature called 'collections'. A souped-up bookmarking feature: visual links, images, notes. Also, Edge lets you edit and annotate PDFs. (Chrome and Firefox display read-only PDFs).

This random YouTube video makes a case for Edge 'collections' and PDF features: https://www.youtube.com/watch?v=5fjwNMyHWCY&t=152s