Try Lanes - https://lanes.io. It combines tasks, bookmarks and video annotations and uses the Mercury API under the hood.

Disclaimer: I made this. We've nailed down tasks and now we're focusing on making the read-later/bookmark feature top class. Articles are highlight-able and you can reference articles as tasks (because 'read this article' is a essentially a task) - we find this helps you read more, as most bookmark managers are essentially "here's a thing I like enough to save but will probably never read".

Give it a try.