You are examining Factory Combis, and are wondering how KARMA settings such as turning a drum's kick and snare on/off with the Joystick have been accomplished by the programmers.
Examples: A023 Fusion in 7/8, E054 Hip Hop Fugue
There are 4 rows in the DynMIDI Page (6.4-3). These correspond to Dyn1, Dyn2, Dyn3 and Dyn4.
When you set a DynMIDI Row destination to "RTParm Ctrl", you are routing that row into an internal "matrix" of possible Control Assignments for the GE Parameters. Go to any GE, on (6.3-1) for example, and scroll through the choices that are available for the Assign field. First are the 8 Knobs, then the 8 Knobs again (with a special variation that lets them function as 2 position switches only), then the 2 switches, and then - aha - Dyn1, 2 3 and 4.
So any GE Parameter can therefore be assigned to be controlled by a DynMIDI row in this fashion.
For example, in Combi A023 Fusion in 7/8, if you go to 6.3-1 [K GE] [GE P..4], and then press F6 or F7 until Module D (the Drums) is shown, you will see that GE Parmeter #3 is assigned to Dyn1. In this case, the Joystick -Y which is assigned in DynMIDI Row 1 is set to turn Drum Pattern 1 (the kick and snare) on and off.
All you have to do to assign/unassign DynMIDI to control GE Parms is to look for Dyn1, 2, 3 and 4 assignments, remove them, add them, change them, etc.