Yubikey recommends that you register multiple keys, to deal with possible future loss of a key. The procedure for setting up a YubiKey for second Level Authentication on 1Password calls for you to Enable Two Factor Authentication. That step apparently triggers off the next step, but when I try to register the second key, Two Factor Authentication is already enabled, so I can't do it, and I don't see any way to proceed.
I may be missing something, but I don't see any way to register the second YubiKey to 1Password. Is it not possible?
1Password Version: 7.3.657
Extension Version: Not Provided
OS Version: W10 Home Version 1809 build 17763.379
Sync Type: Not Provided