Reverse Animations?

I often use the Custom animations to slide items on and off the screen.

Right now, I place the item where I want it to end up on the stage, add the animation to the timeline, move the playback head to the start of the clip before the animation, move the item off screen, copy that frame's properties, add another animation at the end, and then paste those properties at the end of the clip. It's a little cumbersome. Is there a better way?

It would be great if there was a way to just 'reverse' a custom animation so that the starting and ending XY coordinates are flipped...