You can easily add vendors to the RFQ who are approved for selling at least one of the categories you’ve specified on the RFQ lines.
if you will click on it nothing will happen.
To make it effective you need to make a list of approved vendor for particular category/item
Once relationship created then select the particular procurement category in the line and on vendor selection screen click on the Auto Add Vendor. It will save user data entry time and will improve the data entry accuracy.