Clone your Machine (VirtualBox)

It seemed so easy, but it turned out not to be. After using Export/Import once, your disk image gets the internal UUID from the original. You cannot clone your baseline once more, as the UUID is already being used.
You will have to fall back to the CLI, and issue

vboxmanage clonevdi

That will clone your virtual disk. You still have to create a new Virtual Machine (VM), and attach this disk to it. The cloning part takes some time, the rest is peanuts.