"Plant" screen field in t-code ME41 - Create RFQ

Dear SAP experts,

When creating RFQ, "Plant" field will be disabled (gray / display only) after specifying the RFQ item(s).

This condition still happen eventhough the field screen configuration is set optional for field "plant".

Config path:

Materials Management > Purchasing > RFQ/Quotation > Define screen layout at document level

Is it possible to make the "Plant" field to be editable after specifying the RFQ item(s)?

Please advise.

Thanks before.

Regards