Without a plugin, you can only use the predetermined keyboard keys. As I said, the Escape key on the keyboard is the equivalent of the X button on the gamepad, and the Space and Enter keys on the keyboard are the equivalent of the C button on the gamepad. That's why they are called
buttons and not
keys. I don't know what the Z button is. I guess just keep pressing every key on the keyboard until your text for the Z button is displayed, and then you'll know what it is

Maybe it's the shift key?