I tend to make a lot of lists and find that even many completed to-dos with strike-throughs makes a list busy and sometimes difficult to surface the un-finished tasks. Could we have an option to collapse or move completed to-dos? Even better would be if Agenda could tell that the to-do list is part of a Header or Sub-heater and collapse (or move) to the bottom of just that section it belongs to. So there could be two approaches here and maybe both available as options.
Collapsing completed to-dos: move to the bottom of the list and not visible until a toggle is pressed.
Moving completed to-dos: show them as they are now with strike-through or grayed out, but move them to the bottom of the list.