Hi @Christina_Harris1, welcome to the Asana Community Forum! As it stands, for Rules to apply to subtasks, you need to add the subtask to the project. We don’t have immediate plans to create a trigger to take an action on subtasks, I recommend you adding your vote to this thread and we will make sure to post updates as soon as we have any: Allow Rules for Subtasks
Thanks for your feedback, @Marek_Cevelicek! We will definitely start leveraging more the tags function in the forum to give more insights about the product updates.