Create new field based on existing fields from dataset

How can I create new filed with type Map using values from existing fields. For instance I have fields client_name, client_id. I would like to create new field client:
{ “source_system_client_id” : “client_id”, “name”: “client_name”}


Currently Dremio only supports STRUCT or LIST complex data types

How can I create similar structure type { “source_system_client_id” : “client_id”, “name”: “client_name”}
using STRUCT or LIST data types based on available fields in dataset client_id, client_name