What you can do graphically with a slider component, you can now do with PowerShell, programmatically, for the use you may think of.
-Run the brightness.ps1 scpript in PowerShell.
-The script will show the actual brightness level on your display and prompt for a new one.
-Type the desired brightness level, from 0 to 100, and press enter.
-Display will change brightness and PS will show the new level.
The intention is to have access to this feature programmatically, in case it is needed.
-Only tested on Windows 10.
-Script uses WMI which is deprecated by MS. Migration to CIM/WS-Man should be considered.
-May need to modifiy execution policies. RemoteSigned worked for me: Set-ExecutionPolicy -ExecutionPolicy RemoteSigned