The single knob cycles through 4 compression/ saturation presets (A, B, C, D). A & B are more aggressive; C & D are smoother.
Go to Options → Preferences → VST → click “Clear cache/rescan” . soundgoodizer reaper
Click the FX button on any track → search “Soundgoodizer” → add it. The single knob cycles through 4 compression/ saturation