But to my thinking the easier method would be to add all three clips to the same Master timeline and just Crop and Position them as needed.
In my case, I'm attempting to split-screen 3 sequences of shots, not merely 3 individual shots. So adjusting the scale, position, and crop parameters for each individual clip would be incredibly imprecise and take an extremely long time.
When I attempt this, I am getting a different aspect ratio for each of the 3 nested timelines. All 3 of the nested timelines have exactly the same timeline settings and scale/retime settings within the inspector window.
Going through the color page is an interesting hack, but what is the official workflow for this nesting process with timelines of various resolutions?