Indeed, I still wonder why its not there since the beginning. Look at https://bugzilla.mozilla.org/show_bug.cgi?id=196509, this demand is 15 years old ... and there are others asking for the same kind of functionality, they are between 9 and 18 years old ..
I guess it will come one day .. but as I didn't want to wait, and since I didn't want either to stick to old versions of FF, I decided to give it a go :-)
