Reopening this as the old request was marked "closed" on the basis that the app was being redesigned and devs were "considering it" - which is not good, by the way! Please don't close support requests unless they're actually resolved, either by being fulfilled or eliminated as a possibility.

We badly need an indicator on a task that it has subtasks - it's impossible to tell without clicking on every one, and there is not warning if you try to complete a task that has incomplete subtasks.