Can a custom value be added to the legislation code

Summary:

We have a UK client who is migrating data for passports from EBS to Cloud HCM. In the original dataset they do not have the issuing country or legislation codes recorded for the passport.

I have looked for a way to add a custom value to the lookup that contains the country list but can't see a way to do this, is it possible to add a custom LOV value to the lookup that is used for passports in order to load a generic value to get these passports into Cloud?

This question asks a similar thing about which lookup is used.