Hi,
I'm not exactly sure what you are trying to do.
You want to be able to press a key on your PC/Laptop and that will tell the controller to up or down LED brightness.
Senario 1.How will you distinguish say pressing "u" on your laptop, when typing the word say "understand" in a word processor app, and not have the LED brightness increase?
I would just have a separate window open with serial monitor or putty or TeraTerm terminal app running to send my LED commands the controller USB.
Another suggestion, use an ESP32 as your LED controller/web server, and open a browser window to send commands over WiFi.
Your Laptop app can be two buttons you click with the mouse.
First can you explain how to over come scenario 1?
Tom... 
