@PH1975 Interesting! So your note prompted me to recheck the manual for my set.....because I’m the kind of guy who actually reads owner manuals and I wanted to know if I missed anything before asking the forum and wasting your time.
The only section I found is the one I read before, and it is silent regarding middle unit lights and couplers altogether. The older manual you have was far clearer than the one in my set.
“TrainMaster Command Control allows you to couple your Command Control-equipped
Tlocomotives together, forming a multiple unit lash-up. Just like with the real railroads,
lash-ups allow you to pull longer trains and climb steeper grades. You will find that the lighting operates prototypically—the lead unit’s headlight and interior lights are illuminated when the train is in forward, and the rear unit’s headlight and interior lights are on when the train is in reverse.”