It is really difficult at the moment to extend the Shopify integration in Business Central for customizations.

For example you can't hook into add anything to the graphQL json for custom fields.

You can't access any functions in codeunit 30103 "Shpfy Communication Mgt." to call any custom graphQL methods or write to the error log table.

Seems this is by design but it really does challenge the usefulness of the Shopify connector redundant in partner implementations.