Based on a quick look, the biggest features it has that browser bookmark managers generally don’t have is the ability to search within saved webpages and documents without opening them. Plus, you can share bookmark collections with other people. Sounds a bit like a modern rendition of del.icio.us

Yup, it’s this one. I personally use it, and it makes the YouTube experience so much more enjoyable. It takes a second to get used to the UI, but it’s amazing once you get the hang of it

If you did want to skip sponsored content within videos, try using SponsorBlock. It’s an extension that skips ads, transitions, and other annoying segments within videos based on user submitted timestamps. Pretty much every YouTuber I’ve found with over 100K subscribers has already got segment timestamps on most of their videos. It really makes watching videos more enjoyable