How to add custom fields to SOCO & enhance search query

Dear SRM Experts,

I need your guidance.

We have a requirement to add few custom fields in SOCO based on which buyer can search the desired Shopping Carts. The custom fields that we intend to add as a search criteria are all Shopping Cart header fields:

I have below queries:

1. Can we add Shopping Cart Header fields in SOCO as search criteria? I have a doubt because Shopping Carts line items appears in SOCO.

2. Is it POWL that we need to enhance, if yes how can i search which POWL is it

3. If its a direct WebDynpro Enhancement what should be the approach and how to modify the search query.

Awaiting for your feedback.

Thanks & Regards
Punit Jain