View the Lists within a Folder. If the Folder is a subfolder, the response includes a parent_folder field with the parent Folder ID.

Use the include_subfolders query parameter to include a folders array in the response. Each entry is a complete Folder object with the same fields as the Folder you requested, including its own folders array, so the response contains the whole subfolder tree down to the Workspace's subfolder nesting limit. Subfolders the requesting user cannot access are excluded.