The Asko/ASEA/Cylinda dishwashers I had a curiosity in back in 2012 (that is, the DM1302/1402 and computerised 1502) were all products of the early 1990s. Interestingly enough, these all featured a plate-warming cycle.

The more BOL machines had the Drying Phase selectable on the timer, whereas the digital model had a selectable cycle. 

All machines were fitted with a 1200w heater element in the bottom of the tub for water heating and drying. There was no "forced air" drying. 

All these machines were of European descent, and even marketed here in Australia. In both instances, our energy costs are drastically larger than those in the US. 

I think US machines with a manual-timer could be run on "plate warmer," although you'd probably need an empty dishwasher, run through a rinse/hold phase first...