The option to Alt+Ctrl drag keyframes and have them retime from the centre rather than the start or end.

Often, you have an animation happening at a certain time, maybe text in and text out. And it would be MUCH more convenient to retime keyframes from the centre, not the start or end.
Having a modifier for this, so ALT does normal behaviour, ALT + CTRL re-times keyframes from the centre - almost like it does when holding CTRL while scaling a mask or path selection.