If your extension have gschema.xml file.. and after successful installation of the extension, if you dont find the gsetting keys mentioned in the gschema.xml file.. It indicates that the gschema.xml file is not compiled while the installation process..
In such case.. you need to manually compile the gschema.xml which is provided with the extension.
to compile the schemas.. first copy the gschema.xml provided by the extension, to any of the folder mentioned below..
$HOME/.local/share/glib-2.0/schemas/
/usr/share/glib-2.0/schemas/
Where to copy in above two choices is self explanatory.. first one for local or per user based.. second one is global or admin based..
to compile the schemas.. run the below command from the any directory mentioned above.
glib-compile-schemas .
Example:
As a local user
cd $HOME/.local/share/glib-2.0/schemas
glib-compile-schemas .
for global or as a Admin
cd /usr/share/glib-2.0/schemas
sudo glib-compile-schemas .
Note that, In a default installation $HOME/.local/share/glib-2.0/schemas will not be available so you need to create the directories first with below command
mkdir -p $HOME/.local/share/glib-2.0/schemas
Similarly when you delete the extension or you want to remove the gsetting keys..
Delete the file gschema.xml and then run the glib-compile-schemas command.