iMovie SplitScreen & PiP plugins for Mac

From Stupendous Software:

This iMovie plugin package includes effects for combining multiple clips into split-screen and picture-in-picture configurations. Two or four clips can be combined into a split screen in one pass, with control over the split directions, proportions, and edge softness. Picture-in-picture images can be created using one or more passes, and the smaller image can be placed anywhere in the frame, presented in the original shape or as a circle, and have hard or soft edges.