Hi @KimberlyAnn_DiCredic , it sounds like you found what works for you and that is why Asana is great, flexible for numerous ways of doing things. But it seems like you definitely hit a limitation!
So I ran a quick test using the CSV importer to create subtasks into a task and view it in Timeline. It appears there is a limit of 50 subtasks that can be visible within a task. 
You should see a blue link at the bottom of your expanded task window saying ‘View all subtasks’ which then opens the task details pane. This limit is likely set for performance reasons.
Thanks for raising this, I will be adding it to my post, 🔢 List of technical and data limitations in Asana