In Designer ClientBluetooth.DelimiterByte : 10
In the example of @uskiara in Designer Clock Enabled.
Comment out all // Serial.println except Serial.println("j");
What do you get on your Serial Monitor when you press the joystickbutton: buttonState?
What Arduino terminals do you have the BT module connected to?
How many bauds is your HC-05 set to?
More examples: