Ok forget this. Don't use that extension. It's much easier!

When you're connected with your Nostr id you can find an article, open it and start highlighting. In the search input element you can submit any url with a reader friendly format attached to it.

Just tried it out with my latest blog item: https://highlighter.com/load?url=https%3A%2F%2Fsebastix.nl%2Fblog%2Fwhy-nostr-resonates%2F