Comments

Steve Grisetti wrote on 2/12/2016, 1:24 PM
Not that I know of.

But it would make more sense to use the Pan and Crop effects.
autopilot wrote on 2/12/2016, 7:14 PM
Right click on transition, then insert envelope, transition progress. Maybe?
astar wrote on 2/12/2016, 7:35 PM
Keep your media PiP and split screen media on separate tracks. Then use Track Motion at the track level to key frame the effects. You can use a 3rd track as a background for the split screen, for example the way CNN does.

If you cannot figure out how to control the transitions, render the PiP and Spit screen footage to an intermediate. Then transition as you normally would.
Chienworks wrote on 2/12/2016, 8:10 PM
Agree with astar. One you get a handle on using tracks, track motion, and pan/crop, you'll find it faster, easier, and much more capable than using transitions. This sort of thing really isn't what transitions were made for.