With this module dedicated for prestashop you can disable group discount (defined for group of customers) when customer's cart will contain voucher code. This means that prestashop will not use both of these discounts - the only one applicable discount will be a discount from cart rule (voucher code).
As you already know, with this module you can easily disable group discount (defined for customers' groups) in cart that will have a voucher code. This means that only one applicable discount will be a discount that was defined by cart rule (voucher code).
1.1.1
1.1.0
1.0.0