Why can't I change the suggested buyer from my smartform?

Summary:

I am looking to change the suggested buyer, but I only have the option when I use the Enter Requisition Line page. I do not have the same options when I go to enter a requisition from my smart form? How do I fix this, I need to be able to edit the suggested buyer from a smart form entry.

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Version (include the version you are using, if applicable):

Responsive Self Service Procurement

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