I have a VirtualBox virtual machine that I wanted to rename. I tried by editing my config file, and when that broke things, I searched and found you don't want to be editing VirtualBox configuration files with Vim: you only want command line and GUI files.
I have what I am pretty sure is the exact disk, unmodified apart from possibly having the UUID changed from a VirtualBox command line files.
How can I create / restore / modify / ... a virtual machine with VirtualBox that will have my .vdi file as its disk?
You should be able to create a new Virtual Machine and set the .vdi as its hard disk.
https://blogs.oracle.com/oswald/importing-a-vdi-in-virtualbox