this is probably one of the best extensions I've used, with features that are useful, obvious & intuitive right out of the box.
I have a few extensions that I install on every browser, and this will be one of them

it should be preinstalled, way better than the usual tabs

多段タブがバージョンアップのたびに使えなくなるので見限り代替となるものを探していました。

please make it possible to hide the original firefox tabs

The number 1 reason why I use Firefox!