Use existing MacOS volume as VM (like Bootcamp)

I posted this a few days ago but it seems to have been deleted so trying again...
I have created a dual boot machine so I can boot into Mojave normally or into High Sierra (by holding ALT during boot) so I can run older software that is not compatible with Mojave. Now what would be really handy would be if I could use that High Sierra Volume as a virtual machine (without having to create a new Virtual machine that takes up precious hard drive space). You can do this for Bootcamp where the same bootcamp partition is used both when you boot and when accessing it from Parallels. What I'd like to see is the ability for other Mac OS volumes to work in the same way.

This would allow us to boot into the same virtual machine depending on whether we want to harness the full machine's resources or just use Parallels to do some light work while still in the main host operating system.

If this feature already exists could someone tell me how to do it?

Thanks in advance.

 

this idea is one I have looked for every year or two, but it doesn't seem to be possible yet?

 

My Mac Pro 2008 died. It had all Mac OS X versions from 10.4 to 13. I moved the SATA SSDs to my newer Mac which can't boot all of those Mac OS versions so I tried Parallels. First I construct the .hdd manually with a custom DiskDescriptor.xml . Then I assign it to a virtual hard disk of the VM. When I try to start the VM Parallels complains about invalid BootCamp partitions. It only allows NTFS and FAT partitions to be used this way.

VirtualBox has a command to create such disks. You just specify the disk and the partitions you want to include. It looks like this:

Code:

sudo VBoxManage createmedium disk --filename mypartitions.vmdk --format=VMDK --variant RawDisk --property RawDrive=/dev/disk7 --property Partitions=1,13,14

Why can't Parallels do the same? I have to manually copy my partitions into separate disk images so they can be used with Parallels.