Desktop live tile is greyed out in Start screen while I am in Coherence:
In Parallels Desktop Control Center Windows virtual machine is also greyed:
Windows virtual machine does not have a separate Desktop while it is in Coherence. Coherence allows you not to switch between windows and to have one integrated Desktop screen for both Mac and Windows OSes.
If you click on greyed out Desktop live tile Mac OS Desktop screen will be showed up.
The Desktop live tile is available only in window and Full Screen modes. To switch into please follow steps below:
Exit Coherence (right-click on Windows icon in Dock > View > Exit Coherence).
Go to Mac menu > View > Choose the preferable view mode.