Last time I tried that meant having to do a rather slow and disk hungry export followed by an import. Was I doing it wrong and is there no way to just copy the disk and machine definition, or are there other ways already?
If I need to move a VM for some reason, I copy the entire VM directory to the new location then open VirtualBox and use "Machine" -> "Add ..." and select the directory with the VM config and files.
I hope that helps, unless I missed something.
Does this work or could the VMs get corrupted?
Host volume mapping is a folder shared between the host and the VM?
Yes.
Hosts:
Notebook runs Linux Mint 17 with VirtualBox 5.0
Desktop runs Windows 7 with VirtualBox 4.3 (5.0 ha an issue on Win7 that Oracle won't fix, but prevent my VM from starting)
Guest:
Xubuntu 15.04 with the VirtualBox 5.0 Guest Additions