I rewrote the codebase in React.js and TypeScript. I also rewrote all the styles using Tailwind. I did this as a learning exercise. The old codebase was written in pure JavaScript. I didn't use jQuery or even promises. It was incredibly difficult for users to contribute due to its complexity.
There's one feature that remains to be migrated: "Tab snapshot overwrites" which allow users to change the contents of a tab snapshot. I never implemented any telemetry into the extension, so I'm not sure if it this feature was actually used. The app at the moment has ~170 daily active users.