Restrict categories to End users/Buyers for non catalog orders

Summary:

We use certain purchasing categories which is primarily used by the downstream application for creating PO and interfacing back to Fusion .

So we need these categories only for PO integration purpose and we dont want these categories to be visible for the buyers/end users at the time of PO/PR creation . Is there a way to restrict it for non catalog orders without smart forms.

I came through older post but dont see any solution ,pls advise.

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