I've never used Vegas' Nesting...
This video is perhaps an age-old hackneyed idea of the bouncing ball on Karaoke-style music lyrics. Don't pay too close attention to the animation - it's just an experiment.
First, I created a single track with a gradient solid on it (white-red-black, ellipse shape) and then used the Pan&Crop tool to create a 'ball.' I then selected the event and created a Nested Timeline.
Using the buttons at the bottom, I opened the newly created nested event for editing and added Track Motion for the vertical movement. Then clicked the button to go back to parent and added horizontal movement also using Track Motion.
That's basically it...
For more information on Nested Timelines check out the help file.