Thank you for posting your query on Microsoft Q&A.
Based on your query, I understand that you would like to add Apigee to SAAS application.
To implement SSO for a SAAS application, you need to configure the application from Enterprise applications in Entra ID. Here is the Microsoft document to configure an application: Add an enterprise application. You can also go through this document for an overview of adding different kinds of applications in Entra ID.
Adding Apigee layer to SAAS application is currently not available. Apigee is currently used for Azure APIM, which is added as a tool for migration. Apigee acts in different scenarios and here is the configuration you can do with Apigee: Apigee to APIM migration tool
But you can provide your idea in our feedback forum link which would reach our product team where if there is any higher requirement on the same, they would go for any possible implementation.
I hope this information is helpful. Please feel free to reach out if you have any further questions.
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