Lock your WooCommerce coupon after printing it on physical marketing materials or announcing online.
This plugin creates an additional widget on your Coupon editing page with Lock / Unlock.
After locking, the critical Coupon fields are disabled for editing, i.e. Title, Discount type & amount etc.
Optionally specify locking reason for your own notes. Reasons are then shown in the Coupons table, in Locked column.