Previously on HN: https://news.ycombinator.com/item?id=9845301 https://news.ycombinator.com/item?id=9845301 I've been really looking forward to this, because

Previously on HN: https://news.ycombinator.com/item?id=9845301 https://news.ycombinator.com/item?id=9845301 I've been really looking forward to this, because tree style tabs are the main thing keeping me on firefox. But now it looks like in-window sidebar extensions aren't going to be possible.