You can only apply one discount code per plan, product or event. However, there could be a use case where you need to add more than one discount to a Members plan. Here is how you can do that.
Method 1. Modify base plan amount
Use this method if one discount should be removed after certain amount of uses and the other discount is staying. A good example is a member with a Family type discount that always stays on, but you want to stack on to that a referral discount which is only good for 1 billing cycle.
Modify the base plan amount by clicking on plan context menu and selecting 'Change Amount / Discount'. (from member profile page)
Change the 'Subscription Price:' to equal the normal price of the plan minus the recurring discount, in this example it would be the Family discount.
In the 'Change Discount To:' dropdown, set this to the referral discount.
Method 2. Create a combined discount
Use this method if both discounts will recur forever or same amount of time and its a common scenario that you might use often.
Create a discount code that is the combination of the 2 or more discounts you want to use.
Add this discount by clicking on plan context menu and selecting 'Change Amount / Discount'. (from member profile page)