You can't return data in response mappings for NetSuite imports. Our suggested workaround is to add a secondary lookup step. Any field returned by an API in the context of an import is available in your response mappings. The fields you see by default in our UI are universal for all imports, but you can map any other fields that you know should be there.
For example, if an API returns a field 'banana' in a POST response then you can map this field 'banana'. In the JavaScript post submit and post response map hooks. Use the field called '_json' as a container for all fields returned in the response from an external API.
For more information on lookups, see Response mapping and advanced lookups.
For more information on hooks, see Hooks for integrator.io.