It works fine, however if u use the containers (which I do) it doen´t work with it... it only loads the selected site on the standard option. If u click on it with the middle button, it opens the firefox normal page... very sad... I hope u guys can find a solution for this!

When using the setting to not close the window when closing the last tab, three tabs are opened.

Example: https://media.giphy.com/media/xbsW77Add9mtW/giphy.gifv