With Keyboard Shortcut
If you want to adjust the brightness of your Desktop using keyboard shortcut like laptops, then you cab do this by using a software called 'Desktop Lighter'.
Steps 1 : -
Download Desktop lighter from below link.
Steps 2 : -
Steps 3 : -
Steps 4 : -
* Your Keyboard Shortcut to Adjust is Ctrl + <> ( while pressing ctrl press '<' and '>' to adjust brightness)