I am trying to develop a public app for free shipping bar something like free shipping bear. I dont know how to update the shipping bar text on frontend, According to the cart items of the user. I am using core php for app and shopify cli to create the theme app extension.
Not very familiar with App development but would it be possible to Cart Transform GraphQL to help you out?
If not maybe there’s some kind of webhook in the API you can take advantage of.