Unique ID Field Not Visible When Creating Transaction

Hello,

On the SA_TRAN_ITEM table, there is a field called UNIQUE_ID which is meant to be where the serial number goes for an item during a transaction.

However, when we are creating a transaction, there is no field with the name of UNIQUE_ID, and we don't see a place where we can enter a serial number,

Is there a field by a different name that is dedicated to the unique ID/serial number? If so, which field is this?

Thank you!

Claire