Where's the Button? Rated 1 out of 5 stars

I installed it, but see no button. And the info page doesn't even say what the button will do, even if did show up. Do you assume everyone already knows what it does? Why is there so little information, and where's the button supposed to even be?

I've added an image with the button highlighted. This addon basically sets the list-all-tabs button to be always visible.