Promotion codes - Automatic release
Promotion codes should be reactivated automatically (when an order is cancelled).
Example: An order (with promotion) was set to cancelled after a certain time. Unfortunately, the code still has the status "used". After such or a similar cancellation, the code should automatically be released again.

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Christoph Von Heydebrand commented
When you create individual codes for your customers (e.g. birthday discounts, etc.) and the code is used, but something goes wrong with the order (e.g. payment gets aborted) the promo code is marked anyway as redeemed and cannot be used again by the customer, even though the initial purchase was not successful.
This results in angry customers, who understandably contact customer support, which then forces customer support to apply manual effort to either create a new promo code for the customer or manually making the already used code redeemable again.