Making "On/Off " button visible

Hi everyone! 

Today i recognized that gnome-shell-extensions only can be activated
with firefox (and google chrome i guess) but not with opera web browser!
When opening the 'alternate tab' extension
("https://extensions.gnome.org/extension/15/alternatetab/") for example,
you won't see any on/off button beside of the extensions name. Even
bringing your mouse-arrow over the place where the button is supposed to
be won't make any different. The only way to install a
gnome-shell-extension is by downloading the archive via github and
packing it as a zip-file, which is kind of complicated. Could you make
this button being visible for opera users, please! I'd be glad to hear
from you. 

Cheers!
Jonas