Excellent and simple

Did what it says it does.
Works out of the box.

Once installed, on the list of all coupons, you’ll see a third option when you hover a single coupon, besides Edit and Trash there will be a Copy action.
Once copied, the new coupon will be opened so you can immediately edit the title of the coupon.

I’m a developer and have inspected the code which is neatly organized and I didn’t encounter any errors/issues while running the plugin.