Hi all,
I created a Google Chrome extension and implemented the button to convert the task to a subtask of another task.
They don’t need to be in the same project or in the same view. You can reference any task in Asana Workspace/Organization as the new parent task.
(Which means you may need to remove the project from the subtask manually.)
If you are using Google Chrome, you can install the extension from the Chrome Web Store.
More info on this Asana Community post: Efficiency Google Chrome extension to enhance navigation for Asana tasks.
Hope this helps.
Best regards,
Shun