Store named volumes on another drive
If I understand Docker Desktop and Hyper-V correctly, volumes are stored inside a MobyLinuxVM.


That's right and it seems to be possible to  move the whole VM to another drive as described here. 

Maybe you could solve you problem by using a volume driver as described in the official docs. 

Another approach is to use a Linux VM with Docker and tell your Docker on Windows installation to use another daemon by setting the DOCKER_HOST environment variable. This will give you more control and will allow you to use everything available on Linux (mounting, symbolic links, ...). But of course this will not work if you or your IT department want to use Windows containers some day.