The discounts and surcharges module has a lot of features: use it with care. If your discounts and surcharges rules are too complex it will be confusing for your customers and unpredictable what will happen when discount rules and conditions are combined. The number of testing paths becomes too big which makes it impossible for us to offer technical support for combinations of more than 3 discount rules.
In order to not limit our customers we allow to add more than 3 discount rules.
Add more than 3 discount rules (technical support does not cover in this situation)