"My dishwasher has a little container for detergent which has
a cover that opens to let it out. It can open but never close by itself. I
load detergent the first thing before anything else, so if I open the
washer and the cover is closed, it means it's still dirty. Indeed, you
still need to open it but you don't have to scrutinize the actual load
"If I had a reversible sticker, I'm guaranteed to forget to flip it when
needed. The detergent cover is a better indicator for me. Granted, I only
have to look at it a couple of times a year, mostly when someone else
loaded it for me, which is rare."
I'm with you, I would be sure to forget the magnet, so I fill the powder dispenser the first time I put a dirty dish into the dishwasher.