Running VIP Authentication Hub, and developing a self-service application to enroll the end-users, a given user can have multiple TOTP and/or Push setups.
Why out of box inline enrollment flow supports 1 PUSH or 1 mobile OTP per user?
Where as a user can register multiple PUSH or mobile OTP credentials using self-service flow?
The In-line enrollment was designed to allow the user to register a missing credential required for authentication. It was not built to be an all-purpose credential registration flow. That's why the API's and created a demo self-service portal as part of the sample app. This is by design.