I can assure you I am an expert on licensing, and your statements above are not relevant to my request.
Regarding licence transfer, it very much depends on source and target devices. What is little understood is the licence transfer mechanism was introduced to enable users to transfer licences to a new motherboard in event of failure of existing mobo. It was not to allow wholesale transfer of licences to a new pc like a retail licence. So if the new device is to different to the original, MS refuses to transfer the licence. i.e. it is likely to refuse transfer between a laptop and desktop. You certainly cannot transfer between a physical machine and a virtual machine.
In the end, it is very hit or miss.
Also, people do not realise it only works if you use same MS account on both devices and are not using local accounts,
Anyway, I am not talking about licence transfer but merely attaching a virtual hard drive to an existing device. As I said the only EULA restriction is you are not technically permitted to have two installations on same pc without a separate licence for each. However this EULA constraint predates Windows 10 digital licences, and it is absurd, because if you install a second instance, it activates automatically i.e. you are not given an opportunity to enter a licence key for the second installation.
In other words, MS's design means you cannot comply with the EULA even if you tried!!!
As I said, there is no restriction on how many times you change the drive - you are just required to have a valid digital licence, and only one installation at a time. Thus I can ensure you my request is totally legal, 100% EULA compliant (if you remove existing OS drive) , and totally within the spirit of digital licences.
Thus, I repeat, it would be a great development to be able to select an existing licenced VM. Otherwise, the usefulness of Viboot is limited.