futz, go into text-backgrounds, lay down a black Solid color on the first track. Add a lens flare effect, then click on the track Compositing Mode button (the little square with the x in the lower right corner), and choose Screen.

Add a second track below and you should be able to see that the lens flare shows just as though you had added it to the second track. I just found this out by experimenting -- know very little about what the different compositing modes do, but this worked. Now you can just create your effect on the black background and move it wherever you want.