What are GNOME Shell extensions?
GNOME Shell extensions allow customizing the default GNOME Shell interface and its parts, such as window management and application launching.
Each GNOME Shell extension is identified by a unique identifier, the uuid. The uuid is also used for the name of the directory where an extension is installed. You can either install the extension per-user in ~/.local/share/gnome-shell/extensions/<uuid>, or machine-wide in /usr/share/gnome-shell/extensions/<uuid>.
To view installed extensions, you can use Looking Glass, GNOME Shell’s integrated debugger and inspector tool.
View installed extensions
Press Alt+F2, type in lg and press Enter to open Looking Glass.
On the top bar of Looking Glass, click Extensions to open the list of installed extensions.