If the VG program itself is compatible with Win8, so should be the PL Manager.
Folks using it tell that it works, and with no major problem.
Perhaps you should ask from Wyld or Starryk directly, what might be the reason ...
I've heard that Win8 is kinda buggy, 8.1 works much better.
Have you got any error messages, trying to install the PL Manager, or they do install correctly, but just doesn't work?
Edit: Wyld has been told that the download and installation of his Free AddOn on Win8 can be problematic, due to the new Windows Defender's tighter security controls.