Search for logins with authenticator key / verification code (totp)

i am trying to figure out how to search for logins to which i have added an authenticator key to generate verification codes for the purpose of two-factor authentication. i know of the advanced search function, but not how i would go about using it to return all the logins in my vault that have an authenticator key.

i could go through and manually add a custom field with a name or value that indicates whether or not i have remembered to add this custom field to a login that i have added an authenticator key to. but i would prefer to be able to just search for the presence of a non-empty authenticator key field.