Hello. I am having a difficult time adding more than one performance to the superknob without overlapping the voices and to transition smoothly over to the next voice. How do I add additional voices to the superknob?

It is not exactly clear what you mean or what you wish to accomplish. But we have tons of tutorials that go over programming the Super Knob.

I can recommend the following articles: "MONTAGifying Motif XF Performances: "Worship Center" and "MONTAGifying Motif XF Performances: "Dream Ballad"

"Worship Center" - takes four PARTS and shows how you can assign the control to the Super Knob. There is an example download; a MONTAGE CONNECT File (at the bottom of the article to give you all the data you need to learn about programming the Super Knob to control when PARTS come in and how to use the Super Knob to fade them out.
"Dream Ballad" - takes three Parts: Piano, Electric Piano and Strings - and shows how you can morph between Piano and Electric Piano, with separate control over the balance of Strings

The tutorials are in depth, so take your time - they take about 23 and 13 minutes, respectively... but when you complete this you will have a better idea of how to navigate the architecture and how to explore the parameters. There is an entire series of these explorations...

Tutorial articles:
MONTAGifying Motif XF Performance "Worship Center"
MONTAGifying Motif XF Performance: "Dream Ballad"

Here is a Master Link to the MONTAGifying Motif XF Performance series:
MONTAGifying Motif XF Article Series Links

Ok thank you so much .