Is there a fool proof way of seeing all the subtasks of a main task? Frequently it says that X number of old completed tasks are hidden. Sometimes I get an option to remove the filter to see all subtasks, and some times I don't.
Removing the filters is the best way to see all of your subtasks. Although you should know that it is currently not possible to see older completed tasks nested inside the parent task. This is something that we hope to remedy soon.
I think I found a work-around. Filtering issues aside, the problem appears to happen when all subtasks have been completed. If you add a subtask to the parent you will then be able to see all the old completed subtasks.