As needed, you can unassign line items for your suppliers in an RFQ. On the "Responses" tab of the Responses page in Quoting, select the parts and then click on Unassign. The Unassign Items modal will open.
The window will instruct that once you click on Unassign that "Items will be removed from responses page, and suppliers will be unassigned". Click on Unassign again to confirm and finish.