Hi there, we’re already planning on offering it for certain input type, such as email & phone number 
However, they’ll be individual field validation. In other words, if you’ve enabled “Don’t allow duplicated value” for Email & Mobile inputs, then if either value is duplicated, submission won’t be allowed.
We don’t plan on offering “combo” logic at this moment. And to be honest, it’s not ideal for your use case. Either Email & Mobile alone is already a good client identifier as they should only belong to one person. You’d know something isn’t right if either value is not unique.
If you only consider it duplicated based on the combination of all 3 value, then it’s going to have the opposite effect (E.g. someone made a typo in one value and the system won’t consider it duplicate 
)