As an example, the code that makes the median renko bars is relatively short and straightforward. What I'd like to know is where to find documentation about many of the NinjaTrader namespace method calls used within, such as "AddBar", "UpdateBar", and so forth. It doesn't appear to be anywhere in the 6.5 or 7.0 "Help Guide", but someone in the forum must know.

The best possible solution would be something like Java-style HTML docs for the entire NinjaTrader namespace. With docs like that, you can do anything.

Many thanks for help from those in the NexusFi (formerly BMT) community

Their is no such documentation available.
I presume Ninjatrader developers have is, but this is their internal documentation.