Hello,
In general, one can assign NVDA commands to key strokes within the gestures area of the main NVDA settings. I have no idea what features or documentation there is for the this add--on. But since NVDA does define several keystrokes for displays, I have to assume that at least those keystrokes that NVDA extends to provide some feedback should be easily mapped in NVDA to braille keys.
I decided t follow this thread hopping to hear about the basics of the braille extender but nobody has replied.
Take care!
Jonathan