1. Choose the interval
Create or select the timeline range that should change speed. Speed is applied only inside that interval.
2. Add Speed
Choose Speed in the floating toolbar. A green effect block appears on its own timeline row and the playhead moves to its midpoint.
3. Select the rate
Use 0.5x for slow motion, 1x for normal speed, or 1.5x, 2x and 3x to accelerate.
4. Adjust timing
Drag the effect block to move it or resize its handles to change duration. Zoom and Speed blocks share the same timeline scale.
5. Confirm duration
Review Final duration in Configuration. Accelerated ranges shorten the exported project and slowed ranges lengthen it.