Limit the searchable attributes in RSSP

Hello everyone,

We've enabled RSSP and Elastic Search for Requisitions.

Currently, by default, the searchable attributes are :

• Header: Requisition Number and Requisition Description.
• Line: Item Number, Item Description, Purchasing Category, Manufacturer, Manufacturer Part Number, Supplier, Supplier Item Number, Purchase Order Number, Transfer Order Number, Requester Name, Internal Deliver-to Location Name, and Deliver-to Address for One-time Locations.
• Distribution: Project Name, Project Number, and Cost Center.

I want to know, if it's possible to limit the searchable attributes; as example, only filter by Requisition Number.

Is the search feature not extensible ?

Thanks for your help