# Your locally installed gnome Shell extensions, i.e., these that are installed for your user only, can be listed with the commmand:
ls ~/.local/share/gnome-shell/extensions/

# You can find out which extensions are enables by querying a dconf setting:
gsettings get org.gnome.shell enabled-extensions

# System wide installed gnome-shell extensions are listed with the command
ls /usr/share/gnome-shell/extensions/