How to pass multiple values into Process model without CDT?

Scenario:

Pass multiple rule inputs into Process model without a CDT and pass them individually. Please see the screenshot of user management scenario. As in the screenshot, we are trying to pass userToAdd and groupToADd if selected option is Add user. Since, CDTs can't take User type field and also as we do not want to use CDT as not storing any data in DB, we prefer not to use CDT.

Instead pass values individually. Please advise.

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