Convert subtasks in bulk seems to finally here! I stumbled across it today. Don’t know what release it was hiding under but i’m so glad to ave it!. Converted 6 tasks into subtasks of another task in one quick move! Thank you Asana!
How I did it:
On the list view of my project I selected my 6 tasks.
Then the floating menu bar came up at the bottom.
Clicked the 3 dots for more options
Selected ‘Convert to subtasks’
Typed in the name of the Task I want the subtasks to go under.
Then selected it from the options once it appeared.
Done