Scripting of users of Type "User in another Microsoft Azure AD directory"

Is there any plan to allow scripting of adding users to AAD when the type of user is "User in another Microsoft Azure AD directory"?

We use a second AAD (outside of our primary) for a particular application, and add users internally to this secondary AAD.  We use the "User in another Microsoft Azure AD directory" to leverage the same user id and password for accessing this application.

RIght now, using code, you can create users for the the other drop down options, but you cannot add a "User in another Microsoft Azure AD directory".  You MUST use the user interface to add the users.