Hi there,
I'm glad to hear that you are enjoying our Shopify theme so far.
In fact, Shopify has just made it possible for discount codes to be validated in the cart (not the checkout). Prior to that, that was possible only on checkout or by using an external app with API access. However, we are adding it to the new version that we are just finishing it which will be released soon.
Demo: https://falcontheme.com
For your version, we will provide an update in the future, but for the moment, that is not possible.
But also, it's important to note that the current way, where the users enter their code and it gets validated on the checkout, is not a bad approach, because users are pushed to checkout in a sense. And after they validate the discount, they can simply get back to the store anytime. Based on our observations, it seems that the current approach works fine.
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