add an amount to an existing coupon

Our customer wants to add an amount to an existing coupon. Is this possible?

Hello,

By coupon you mean a gift certificate? If so, you can just edit it and change the value.

Is there anyway this could be done via a purchase, some form of Gift certificate top-up functionality? I'd like to implement something
like that on my site, it would give customers a method of 'saving' towards a larger purchase.

Hello,

There is the balance functionality. So customer can purchase a gift certificate and then add it to their balance:
https://awodev.com/blog/awocoupon-gift-certificate-balance