I can't seem to get a straight answer from SO, the internet, or AWS docs regarding support for multiple SAML (or OIDC) IdP in AWS Cognito.
We have a situation where we may need to have multiple IdP in use with SAML on a single Cognito instance. If this is a problem the project needs to know.
Cognito can handle multiple SAML providers quite easily. When the user logs in they will have to choose which SAML provider, and their user will only be associated with that provider (not multiple).
In the Cognito user pool console go to Federation -> Identity Providers -> SAML There you can add each provider.
If you use the Cognito hosted UI for login, selecting between multiple IDPs is all handled. If you are building a custom UI, you will need to make sure you handle that logic.