Hi, I'm the author of this add-on. It is for sure not abandoned. I was surprised to read that it doesn't work for you, as I'm using it every day. Can it be that you didn't allow the add-on to run in Private windows? Unfortunately this is necessary to be able to list private windows and open new private windows. I've just submitted a new version (1.4), which displays instructions how to allow the add-on to run in private windows. Unfortunately - according to my knowledge - this permission can't be requested programmatically.