It'd be nice to have a way to keyframe the clip speed in kdenlive, similar to how it's done with premeire: https://motionarray.com/learn/premiere-pro/premiere-pro-speed-ramping-tutorial/ As far as I'm aware a smooth way to adjust clip speed over time isn't possible yet.
I change to wishlist. Yes this is not possible so far.
see https://bugs.kde.org/show_bug.cgi?id=418894
*** This bug has been marked as a duplicate of bug 418894 ***