Using Vegas Pro 16 with Windows 10
When I apply the Saturation Adjust plug in to a scene it does not change the color in the Video Preview or external monitor. Nothing happens when I choose the clipboard option and left or right half of the split screen view, no visible change when I put the control sliders to full range.
All other color modifications of different plug ins show up properly on the split screen video preview.
How to get the Saturation Adjust plug in to work properly?
In the VFX window, click on the '?' in the Saturation Adjust controls - its just to the R of 'About'. This opens the user manual at the Saturation Adjust page. Just testing it, the adjusting the Amount slider doesn't seem to do anything by itself. Rather subtle adjustments become available after the Spread and Low sliders are changed from their default.
If you are looking at just increasing the overall saturation of a video event, the saturation slider control in the Color Corrector VFX would probably be a better option.