So our bathroom is <<this>> wide. (That’s 5’4″ me stretching my arms out and touching the walls. Both directions.)
In this comparatively teensy space is a toilet, a shower stall, and a sink/vanity combo. And yet there are two access doors and two light switches.
I know.
The light switch above the toilet is labeled thus:
I… I think that’s just wrong.
As for knowing when the shitter’s full, we have this handy dandy supremely low-tech control panel to tell us:

It’s not always accurate because things get, uh, stuck along the insides of the tanks where the sensors are, so we prefer to go with a weekly dump schedule, just to keep things more… pleasant.