Can you add a custom field on the Parts & Billing section of a helpdesk ticket?

I want to start using the Parts section of the helpdesk system, I've setup the parts list and inventory. Some parts will have serial numbers which I would like to capture at the point of issue on the Parts & Billing section of the helpdesk request. Is it possible to add a custom field to this section?

I tried adding a custom field in the Parts Custom Field section in the setup however it adds the field to the Parts section rather than the Parts & Billing section of the helpdesk request.

I tried adding a custom field to the tickets section under tickets custom fields in the setup however it adds it to the main body of the helpdesk ticket not the Parts & Billing tab of the helpdesk ticket

Any help would be appreciated, thanks