I see that non-Shopify Plus accounts don't have the option to mass load gift cards that were previously issued using a different service.
Is it feasible to upgrade to Shopify Plus for the shortest possible period of time, upload all gift cards via a private app calling the gift card API, then downgrade back to the $79/mo plan?
There is no need to do those changes in your account!
you can use our app - Rise.ai.
In addition to many other features, you can create Bulk Gift Cards in just a few clicks!
Here is an article from our help center
You should check our gift card solution I think you might like it.
Feel free to reach out with any questions at firstname.lastname@example.org