Sonar documentation also just mention that option, without deep explanation.
In the Track inspector and in Console view, in FX Bin module, you can show 4 controls for selected FX plug-in (they change once you select different plug-in in the bin). The choice of parameter is exactly the same as in Automation list. By default it shows the first 4 parameters but that can be reassigned.
I guess that has inspired ProChannel creation: a possibility to control a small set of FX parameters right in the inspector/console, without opening big plug-in GUI.