Kneed beam

This beaming is ugly. My MS has a kneed beam. I have read the manual several times but I do not comprehend how to introduce a knee into this. The Custom Centred Beam dialog is always blank no matter what I do.


This is what I am aiming for:

Do you have to do this by introducing the green voice in the upper staff and moving the notes between staves from the top not the bottom? [Note there are some errors in the MS.]

In theory I think it should be as simple as selecting the three green notes in the upper staff and forcing their stem directions to be down; that should cause the beam to move between the two staves.