Your more complete description of the requirements changes things considerably as you do not want the Arduino to send keyboard commands to the PC, rather you want to send data to the PC via Bluetooth that will be interpreted as keyboard commands.
In order to do that you will need software on the PC that takes serial input from Bluetooth data sent by the Arduino, interprets it as keyboard commands and passes it on to a PC application. None of that requires that the Arduino uses the Keyboard library
Do you have such an application on the PC ?
The Arduino side of things should be easy