Hello,
I don't believe that third party application has been modified to control brightness/contrast through DDC/CI standard in Windows 10. Instead of adding a custom communication, we now use a standard.
We have scheduled implementing the buttons in a different way than Windows 7, but there isn't a solution available yet.
For brightness and contrast, freeware applications like ScreenBright will be able to control the monitor. The application is very old because the DDC/CI standard is not recent. Other applications may be available.
Kind regards,
Alban