In Timeline view, drag the red playhead to the frame on which you want to add a marker.
Do one of the following:
Select Storyboard > Markers > Add Marker.
Right-click in the frame counter area and select Add Marker.
A marker is added in the Timeline view at the exact position of the red playhead.
NOTE It is also possible to add a marker during a playback of the storyboard or to a sound by right-clicking in the the frame counter area. The marker will appear at the exact position of the red playhead at the moment of the right-click.