Multiple discrete inputs overlap each other. It can be difficult to see which ones are on or off.
A couple of DDC systems I’ve used have a good solution to this: each discrete input gets a separate bar at the bottom of the chart. Each bar is the height of a row of text, so its label is beside it. The bar is solid if on, or hollow if off.
It’s slightly different from the other system that I described. The legend is by line-colour instead of beside the binary inputs (which I think is a little harder to read), and it uses an up-down line instead of a solid-hollow bar (which is a matter of preference, both work equally well to my mind).