ScreenFlow User Guide | Main Window : Timeline — Changing Clip Length
| Changing Clip Length You can change the start time and duration of a clip by clicking on the clip near the beginning or end of the clip. When you do this, the Mouse Pointer will change to to indicate you can change the duration or start time. Click and drag to change the start-time or duration. Note that you are only restricting the part of the clip that is played out in the presentation, not deleting anything—just drag out the clip end to restore the suppressed part. However, you cannot drag out the ends beyond the original duration of the clip.