Yeah, I assumed that’d be more difficult so I was trying to reduce scope, but it’d be very cool to see the progress.
The other part, that might be unique to me, is having a box filled with non-to-do cards but still wanting to mark the box “complete”. But I’d be fine sacrificing that if the box could show dynamic progress of the to-do’s within it. (I could handle this with a single checkbox card in a corner)
Edit: I could see the mark all complete being useful (if it doesn’t touch non checkbox cards), but more as a superfluous extra if it’s easy and doesn’t expand scope too much. The progress for the box would be the main win here.
Edit 2: and I think a big part of this, for me, is making sure the progress indicator, when 100% complete, is obvious. Whether that’s fading the box name or crossing it out or something like that so it’s clear from a glance that box is complete.