Oh! I thought “display” was a noun and not a verb. As in “LED Display”. So I tried it, and it’s fascinating. I may have tried it before but didn’t notice the effect so I ignored it since.
Even for someone like me who adores this action, and has read that page many times, it wasn’t obvious what that description was talking about there. Sure I’m an idiot, but I’m probably not the only idiot in the world who needs to read this in the documentation: “the Display option box in this action causes the KM engine to briefly place a green highlight box around the found image. It’s very handy to assist in debugging.”