Hello.
Is it possible to add orders from paid plugins to the store? For example the command "spawnhc uh1y" coming from the plugin "Heli Commander" and which makes spawn a helicopter uh1y.

GUIShop natively accepts console commands from other plugins.

However, if the plugin does not have console commands or they aren't coded correctly to work via third-party plugins then you will have to request from that developer to add support for console commands.