The PriceRule resource now supports bulk discount code creation
API
Effective September 28, 2017
The Shopify Admin API now supports bulk discount code creation. With the introduction of bulk discounts, we will allow a single price rule to be associated with multiple discount codes. Therefore, an app that wishes to create multiple discount codes for a single price rule can perform additional independent API calls for each discount code they wish to create.
Furthermore, we now support the ability to create multiple discount codes in a single request via a new batch bulk discount endpoint. To learn more about creating bulk discount codes, please see the API reference here.
Note: bulk discount code creation is possible only via the API. There is no way to create bulk discount codes via the Shopify admin.