Offers no additional functionality to Firefox that I can see. Every option in this extension is already available in vanilla FF. Sadly, I found this in a Google search for anything, anything at all that would force FF to run in single window mode to stop a pinned tab from constantly opening in a new window. There doesn't seem to be any such option in this extension. In addition, every option that does appear in this is already standard in FF with no extensions at all. I honestly can't understand why anyone wasted their time developing this useless thing.