Nick here from Shopify. Really good question!
I looked into this for you and there doesn't seem to be a way to disable any of the sales channels for an issued gift card. The only thing you would be able to alter is the expiration date
You can see the help guide Shopify has for this going through everything about managing gift cards here.
Can I ask why you would like the exclude the COD aspect of the gift card? The reason I'm asking is that I want to add this as a feature request on your behalf for the future. With more context and the reasons behind this, it helps the team understand how this will benefit your business moving forward.
Looking forward to hearing from you.
All the best, Nick
Thanks for getting back to me with extra context on this. I apologize as I made a mistake, you can edit the sales channels of the gift cards but the COD still falls under "Online Sales" in this instance. If you go to the gift card product page in your admin and then select "Manage" in the Product Availability section as seen below:
You can then select the sales channels you would want this to be sold on by ticking the relevant boxes as seen below:
So in this instance, the only sales channel this would be available on is online sales. I will still add this to your feature request as I can see what you mean.
Thanks again for getting back to me on this.