Welcome to the Asana Community Forum @anon93542219!
Have you considered using rules for this? Rules allow you to create subtasks (or even separate tasks if needed)
So as a trigger you can say all tasks created by a rule automatically get all the subtasks added. Or you can create a trigger combination (for example all tasks created by the rule that are assigned to Person XYZ in section A.
Otherwise you can also have a look at Flowsana and set it up via “Add subtasks from a template” rule action