There is a highlighter extension but I've never gotten it to work (maybe it's just for desktop? nostr:npub1l2vyh47mk2p0qlsku7hg0vn29faehy9hy34ygaclpn66ukqp3afqutajft?)

https://chrome.google.com/webstore/detail/higlighter-extension/hkicahoeiljchfoopjibfdnibceelecp

On Highlighter.com go to Search on input the URL of the website you want to load and then you can start highlighting. Your highlights will show up at the bottom of the page and on your Nostr profile.

You can also try the original site (I believe), zapworthy.com and follow the same process.