Creates a button in the top right part of the GNOME shell top bar. When pressed it turns your second monitor on or off. This is good when you need to save power or focus on your main monitor without distraction.
The connection of my second monitor is hardcoded in the extension.js file. You can change it to yours.
mkdir $HOME/.local/share/gnome-shell/extensions/togglemon/
cp * $HOME/.local/share/gnome-shell/extensions/togglemon/
gnome-extensions enable togglemon
Restart the system (Alt + F2 + r).