Hi All, The rollout of this feature update has started and may be available in your tenant environment. 
Supporting documentation will be provided once the announcement has been made on the Auth0 Changelog, please keep an eye on the changelog page to find any links to supporting docs.
To get you started and test the feature, First turn the Authentication Profile to Identifier First.
Then go to your Auth0 Application and Organization Tab, there you will need to select the Type of Users, and select the preferred Login Flow (Prompt for Organization)