Multiple SERIAL Number Handling

[MadManMoon]

Sorry if I'm being naive, but how would one set this up with two yubikey devices?

Only I'm trying to ensure that from the start both keys can do everything, as I need the backup to be there just in case.

(unfortunately not savvy enough to help with the code, so totally understand if you don't want to answer)

If I were to try to think of a business case, it might be that an admin key would also function.