How can I create a split-screen? I've seen the split screen media generator, but I can't get to to work properly. I only see one video on the split-screen.
How should I nest my two video tracks? And how should I set the "compositing mode" of my parent and child tracks?
No need for nesting or compositing at all. Set all tracks to Source (alpha). Use Pan/Crop if necessary to crop the tracks and then Track Motion to resize and place them in the frame. You don't even need to use the Media Generator.