Set Serial Number as optional in Physical Inventory Count

Dear Expert,

I know that if we set serial number usage in serializing procedure as 02 "Optional", serial number field in physical inventory count (let said MI04) will not prompted. But is there any possibility to enter the serial number as optional? Can't we find the field of serial number though it didn't popup? If it's not possible, do you have any other solution to enter serial number in physical inventory count though we set the procedure as optional?

Your help will be very appreciated and rewarded.

Thank you.

-Stephanie-