Hi @anon52469503 welcome to the forum 
Yes you can ‘multi-home’ subtasks into other projects just like any other task.
Go into the subtask’s details by clicking on the ‘bubble’ icon on the right (or press TAB+right arrow)
Then click on the ... menu within the task details pane and select ‘Add to projects’ (or press TAB+P) and start typing the project you want to add the subtask to as a normal task. You can also refer to this article in the Asana guide.
Hope this helps! Kalimera 