asana.createSubtask uses its parent as the workspace context.
automations/create-asana-subtask.automation.ts
parentTaskId and name. It supports the same assignment, status, completion, custom-field, due/start, description, subtype, follower, and account inputs as asana.createTask, but not workspace or project placement.
Date and description formats are mutually exclusive, as with asana.createTask. Returns the created AsanaTask with Asana’s parent reference when available.