While squaring my frame (sigh) I had to unplug the machine and unscrew the Y-plate. To do that, you have to slide the bed backwards. When I did that, the backlight on the LED flashed even though the system was unplugged. It seems like that shouldn’t happen. I guess be cautious about how fast you move that plate back (although I wasn’t very quick about it this time).
There is not. Most 3d printers don’t have them. It seems like something that should be an easy retrofit, but there are none that I know of, so it’s either harder to implement than it looks (maybe due to loose at best wiring color coding standards or cost?) OR there is some good reason not to add them in.