... why would you want that?

ed.

Hmmmmmm. I can think of two ways.

1) Duplicate the track. Add one transition to one track and the other transition to the other track. Set the opacity of the top track to 50%.

2) Set up the first transition. Render that section to a new file, including at least a few frames before and after the transition. Replace the original clips with the new file. Split at the start of the transition. Drag the end before the split across the part after, covering the original transition duration. You'll now have the new clip fading into itself. Add the second transition to this crossfade. Which order you do the transitions in will probably make a big difference.