When you have a written to-do list on paper, how do you mark an action as complete? Do you cross out the entire line? Or add a checkmark? Or put a tickybox in front of every item in the list, so the tickyboxes for the completed ones get filled in?
My to-do lists look messy when there are many items, some completed and some incomplete, and I tend to rewrite them to clean them up, which is a loss of time if I had a cleaner way of marking which ones are complete and which ones still need me to consider doing them, a way to let me quickly scan the list and know what's going on visually.