Cannot see animated node parameter's F-Curve

Hello Folks,

I am trying to use the Compositor to lay out frames of animation next to each other to make a ‘sprite sheet’.

To do this, I use import image sequence node and then use the translate node to move the image it’s own length every frame by animating the translate X and Y values of the translate node. It almost works, but because the animation by default is bezier, it gradually accelerates and decelerates so that the move of the image per frame is not in whole pixels.

So I go to the Graph Editor to turn the animation bezier curve into linear, but I don’t see a curve over time, I just see a vertical straight line curve on the last frame of animation which does not represent the movement I see.

Any ideas?

Example blend file ?

Select the node.