One of my latest addons has had the unfortunate side-effect that Firefox 46 not has stopped closing, when I first close Firefox and then shut down Windows. So at next launch Firefox will ALWAYS start with saying "This is embarrassing..." and offer me to close this or that page from the last session, before launching. But I say, it is not just "embarrassing", it's ANNOYING!! Firefox never crashes on me, so why should it restore? No, kill that restore!!
Of course the right answer is not
to find whatever addon screwed with my Firefox... So I have looked "everywhere", searching for a default setting called something like "Never restore, just open a new session
". I know it used to be there - somewhere - but now that I need it, I can't find it. Has it gone? No, of course not! But where is it? How do I tell Firefox, to never (try to) restore?