There used to be a Speed effect in earlier versions, and while the Wiki mentions it should still be available under 'motion', the only available option there is Freeze.

While the Speed.xml remains in the folder, the effect is effectively gone.
It has been replaced by a feature in the clip itself; right-click on the clip and select "change speed"
Can also Ctrl+Click and drag the length of the clip itself.

Source: https://www.reddit.com/r/kdenlive/comme ... t_missing/

there are 3 ways to change speed of a clip on kdenlive... the CTRL hot key... the right mouse button on clip (timeline) .. [change speed] .. and directly a generation of a new clip from project bin with the desired speed (clip jobs).

viewtopic.php?f=270&t=165371&p=430720&hilit=speed#p430720