I record a field in my password manager named "MFA". In this field, I record the details of how this account uses MFA. I also have a field named "MFA backup" wh

I record a field in my password manager named "MFA". In this field, I record the details of how this account uses MFA. I also have a field named "MFA backup" where I record something like paper backup codes, and when I last printed them out. I also have a password manager entry for each security key, where I record its S/N if possible (the cut-rate Yubico key doesn't have one!) date of purchase and things like that. I try to make uniform names for them. So far, they're all different models anyway, so I differentiate them the same way I differentiate USB thumb drives, or sdcards. Pretty much anything pertaining to an account, I record it in my password manager. If I purchase a new device, I record its specs, S/N, P/N in the password manager. Everything goes in there.