One (of several) methods would be to first stack the tracks, in sync. Left = track 1, Center = track 2, Right = track 3.
Then use video splits for specific tracks to choose what is displayed. Click the chevron to the right of the SPLIT button to see the many track-specific choices.
Keep in mind that higher tracks override video of lower tracks...
If track one is to be displayed, split out identical portions of tracks two and three, leaving a gap between the splits.
If track two is to be displayed, split out the desired segment of track three, leaving a gap.
If track three is to be displayed, don't split anything, as it will take precedence.