You seem to have copied much of my earlier comment verbatim from https://news.ycombinator.com/item?id=14983976 https://news.ycombinator.com/item?id=14983976 Al

You seem to have copied much of my earlier comment verbatim from https://news.ycombinator.com/item?id=14983976 https://news.ycombinator.com/item?id=14983976 Also, the Tab Groups add-on you've linked still uses legacy APIs, and will not work as-is in Firefox 57, though we're actively trying to design an API that will allow it to work in 57 and beyond.