Here is my attempt to create the broken beam:
In the second beat of the lower voice is an eighth note triplet containing a dotted eighth B♮, an eighth B♮, and a sixteenth C. After selecting the first note in the triplet, Edit > Notations > Beaming > Beam Together is executed. The second note in the triplet has its stem, notehead and ledger line hidden in engrave mode. Then the spacing of the notes and the angles of the beams are adjusted.