The Elastic Stack supports SAML single-sign-on (SSO) into Kibana, using Elasticsearch as a backend service. In SAML terminology, the Elastic Stack is operating as a Service Provider.
The other component that is needed to enable SAML single-sign-on is the Identity Provider, which is a service that handles your credentials and performs that actual authentication of users.
If you are interested in configuring SSO into Kibana, then you will need to provide Elasticsearch with information about your Identity Provider, and you will need to register the Elastic Stack as a known Service Provider within that Identity Provider. There are also a few configuration changes that are required in Kibana to activate the SAML authentication provider.
The SAML support in Kibana is designed on the expectation that it will be the primary (or sole) authentication method for users of that Kibana instance. Once you enable SAML authentication in Kibana it will affect all users who try to login. The Configuring Kibana section provides more detail about how this works.