We have SSO enabled on our APIGEE environment.
If I would like to use openapi2apigee or Management API, is there a document that can help?
You could either use get_token CLI or Apigee Edge UI URL: https://zoneName.login.apigee.com/passcode for obtaining an Access Token for accessing the Management Server:
https://docs.apigee.com/api-platform/system-administration/using-saml