It would appear that this topic has been removed for some reason so I’m reinstating it as it has not been answered.
To quote the Curve Blog of August 2020:
If you have a refund sitting in your Curve Cash card right now, you can spend it immediately but can’t move it to another card just yet. We’re working on making this possible very soon, and will update you as soon as it is.
Here we are over 9 months later and it’s still not happened. That’s a new definition of “very soon” in my book.
If it’s not going to happen just say so.