im sorry i misunderstand ur question workaround for u would be to downlad and install vJoy
and it will create virtual joystick for ur pc which u can control with keyboard
for example u map backspace to virtual joystick button 1 then u just go to 3dnes input mapping and select controller and click on for example button A to remap it and press backspace and now for if u wanna press A button in a game for3dnes it will be virtual joystick button 1 but for u it will be backspace