You can now use the new ReturnReasonDefinition type to capture more granular, category-specific return reasons when managing returns. This replaces the previous ReturnReason enum with a richer data model that helps provide merchants with better insights in their return analytics, and more tailored return experiences for their buyers.
This is a companion discussion topic for the original entry at https://shopify.dev/changelog/new-return-reason-definitions-api-for-better-return-insights