Ubercart Coupon - only allow one coupon per order, but always apply the most recently entered one Currently when someone adds a coupon to a cart which already has a coupon applied, we get the message "This coupon combination is not allowed", leaving the original coupon on the order.

How do we change that behavior so that newly added coupons get applied to the order, while the previous one gets deleted?  There is never a case in which two coupons would be allowed on an order.
The answer is very simple but will only work if you do not want to allow multiple coupons per order.

Visit /admin/store/settings/coupon and uncheck "Allow multiple coupons to apply to a single order"; Save the configuration.  Now the most recently applied coupon will be the only one added to the order.