I can right click on a clip and pick "Show Clip Keyframes" => "Time Remapping" => "Speed" and I can set key frames and everything works but this icon never lights up. Or, I can hit R and drag the clip and change the speed but the icon doesn't light up. I'm just curious if this icon is some left over UI that some developer forgot to remove.
On a different question: once I turn on "Show Clip Keyframes" => "Time Remapping" => "Speed", it has a dot beside it, is it possible to turn it back off? Again... mostly just curious.