Subtask under a Subtask-Section

I am working with the API. I have a task with a subtask-section (subtask ending in a colon). I would like to create subtask under this subtask-section through the API. Essentially grouping my subtask.

I have tried membership, section, and parent options. I am unable to figure this out. Any Suggestions?

Whoa, what an interesting edge case you found here… I don’t know that there is any simple way to do this. You could do a pretty hacky workaround that relies on our insertion order; that is, when you set the parent on a task with setParent it always goes at the top of the list of subtasks. You could get the subtasks on the task, call setParent with "parent"=null on them to unset them, then call setParent again in reverse-sorted order in order to rebuilt the subtasks from “the bottom up”. That’s annoying, but it’d probably work.

The June 26, 2018 API Update announced the ability to sort subtask.
https://asana.com/developers/news