Choose Window >
Advanced Tools. Click the Special Tools tool and click the measure
in question.
Click the Beam Stem Adjust Tool . Handles appears on each beamed stem in the measure.
Drag the handles to the desired location.
For example, stems could be dragged to touch the beam closest to the noteheads,
and not go all the way through the secondary beams. Don’t forget that
you can select more than one handle at a time.