This incredibly useful feature is completely hidden in the Asana user interface and I don’t think it’s documented either, but it’s been there forever and good to remember about.
It looks like this:
The trick to adding a Subsection is to:
- Open the Task Detail pane for the task in which you want to add the Subsection,
- Click to focus your mouse cursor somewhere (any field) within the Task Detail pane (otherwise you’ll get a Section in the Tasks List instead of a Subsection here).
- Use the shortcut Tab+N (the same shortcut that creates a Section when in the Tasks List) to create the Subsection.