I was reading my Dictionary of stops and i cam across this entry for the Physharmonika, which prompted a look up to see what the stop actually was, but the pipe organ that this stop resides in, caught my eye more then the stop, but the pipe organ has a very interesting feature that i need help understanding.

The main console is a IV set up with this odd feature, a secondary console that controls the fourth manual and it comes complete with a pedal board as they say on the web site. What does this really do, in playing the pipe organ?