The Completed Tasks list is a great place to look to see what I've worked on a few days or weeks ago. It's so useful having both future work and past work in one place that if I do any work which didn't already have a Task, I go add one and immediately mark it as completed, just to have that history.

It would be nice if I could do that with a Smart Add function. Perhaps a single tilde (~) or dash (-) could be used for this, representing a strikethrough.