ToDo ver 6 had a nice feature. I could search for the subtask and after finding it I could tap and switch to the parent of the checklist.
For example: I have a checklist called Groceries. I mark completed each subtask that I pick up and the only unmarked ones are what I need next time. Search Milk and un-complete and next time I do groceries it is on my list. If it rises to importance then I can switch to parent task and change date to today and I am all set.