I would also like to see this feature implemented.
Synchronizing the Windows dark/light theme with the macOS appearance setting would be very useful, especially for users who switch automatically between light and dark mode on macOS during the day.
At the moment, Windows has to be adjusted manually inside the virtual machine, which feels inconsistent when the host system already handles this automatically. A native option in Parallels Desktop to follow the macOS appearance setting would make the experience much smoother and more integrated.
I would therefore like to bring this feature request back to attention and strongly support its implementation.
