I noticed that when I launch Gnome Tweak Tool there are several duplicate entries in the "Shell extension" tab:
Shutdown Menu
User Themes
Applications Menu
I checked local and global installs (.local/share/gnome-shell/extensions/ and /usr/share/gnome-shell/extensions/, I hope there aren't any other folders where you can install extensions

Another question: how do you know that there is an updated version of an extension that you installed through the GSE site? and how do you update it, just go to the web site and re-install?
Lots of questions, I know, but I'm completely new to Gnome 3

Ty in advance,
Rehdon