So I tried to get into the 3d mode using my toggle switch set up on my DX8. I am unable to get a 3d response other than lights on, lights back off (B excluded) Even when I try to flick it quickly and try to get that 3d mode whatever it is.
I find it curious that Tamiya would even do this with a 3d mode for one light bulb.
I might just cut the LED off 6 inches back and solder it to A and use them as dual tail lights in my Leopard builds.
I wondered if that B could be a convoy light of some type, on US vehicles from WWII through the 1970s the right tail light was inactive in normal driving mode until you either went into black out mode for convoys, or unless you used the "Park" Feature on the 3 lever light switch then a little white rectangular light on the upper right lights up. I have a couple antique army vehicles so I know how they operate and how they differ from the modern full dual tail light setup Humvees and trucks I drove in the Army now use. Similar, but different.