Since version 20-28, there are six additional parameters that don't have any connection or effect by default. These are the Controls, and they represent the second of three modulation stages.
The Macro Controls are modulated by the Sources, whereas the synthesis engine parameters themselves are modulated by the Macro Controls. The Macro Controls can thus be seen as the hub of the modulation mechanism, which distribute the control movements of the Hardware Sources to the synthesis engine's parameters.
The function of a Control is defined by the sound designer. It acts as a primary tool for varying the sound, as Macro Controls are both interactive (they can be edited) and performant (they can be modulated by the Sources).