@Rovinkind There is no issue with my iOS version. It works right.

@Rovinkind It works on my iPad. On this device, are you using the mobile app or the browser version? There is a slight difference between the mobile app and the web version. On the mobile app, as shown in the screenshot above, in fact you need to scroll the timeline itself, not the yellow marker. On the web browser, you can scroll the yellow marker. On both versions, then remember to enter a speed and toggle the speed switch.