If anyone's still looking, I found an easy manual solution:
1. Exit VirtualBox. It may work while still running but I doubt it refreshes. Probably a good idea to exit first anyway, programs tend not to like their master config files changing under them while running.
2. Backup your ~/.VirtualBox/VirtualBox.xml file then edit it. It's a light edit, any text editor should work.
3. Find the [machinename].vbox XML file in the folder for the VM you're trying to add and open it.
4. At the top of the machine file is a <Machine ... > tag. Copy the whole tag, single line, just the open tag.
5. Insert this into the VirtualBox.xml file with the rest of the <MachineEntry ... > tags, change the name to match. Keep the UUID but change the source to point to the physical path of the [machinename].vbox file that you just opened. I just did some copy-paste with the line above it since I keep all my HDs in one place and follow the general pattern it defaults to. Basically, make it look like its friends but with the correct information.
6. Save, close, restart VirtualBox.
If you get an error complaining about some mounted CD image, edit the [machinename].vbox file and remove the mounted CD/DVD images. This would happen if you've re-mounted the same ISO on the new server as the first time it mounts, it seems to get a UUID that sticks with it. May happen otherwise, dunno, but it's an easy fix. You'll need to re-mount the ISO but that's easy through the UI.
I'm assuming you know XML and can manage modifying a listing while maintaining validity. If not, use an XML-aware editor on the VritualBox.xml file and it should help you. Every XML tag <something> must have a corresponding </something> at the same structural level and <something></something> is syntactically equivalent to <something/>. XML is case-sensitive, even on Windows. If you cronk your config file, you have a backup from step 1.
I did this on Ubuntu but a brief peek at a Windows VBox install seems to show the configuration being exactly the same. On Windows the VirtualBox.xml file is [userdirectory]/.VirtualBox/VirtualBox.xml. Since you copied your machine config from somewhere else, you should know where it lives.
This got me all my snapshots, exact same configuration (minus the mounted ISOs), etc. Took me all of a minute.