If you clone a Windows 7/10 system with clonezilla and store the image on OMV, you could install the clonezilla package (not iso) on OMV (it is in the Debian repo), plug that drive in the server, and write the image to the drive. There is no plugin for this but it would work and is free.
You could also PXE boot the desktop system with clonezilla and write the image stored on OMV to that desktop.
I think I and others thought you wanted to clone the OMV OS drive while it was running.