I know the following should be easy to do, but I've missed something:
Using track motion to lay two tracks side-by-side on the screen. I would like the sharp boundary between the two tracks blended together.
More generally, I'd like to use track motion to have a track on the left-half of the screen, and an empty (or black) right side. I'd like the left side to fade to black from left to right.
I should know this by now, shouldn't I?