Parallels team, see problem report #28297118 (if it contains useful information for this issue). Other users : the VM configuration - Options - Advanced - Activate swiping from the edges (free translation from french UI "Activer le balayage à partir des bords") does not work with PD9 and a Windows 8 guest. It was correct in some previous versions. I tested it windowed and full-screen, could not find any combination of various settings that would get this feature to work.
