Hello everyone!
I'm new to Shopify and trying to create a mobile app front-end with react-native and back-end with PHP. I'm unable to locate some of the main features that can be performed on checkout such as adding ling-items to existing checkout, update the quantity of line-items, get the discounted amount wish is applied on the checkout, add a billing address.
I had been searching for these for more than 2 days but didn't find any solution.
