Custom note group beaming with opposing stem directions?

I'd like to group some 16th notes as in beats 3 and 4 of the first attached image.

I've split the 4-note groups in the second attached image with the "No Beam" option in "Beam Properties" and used the "X" key to flip the stem direction of every other note,

but I can't figure out how to join the stem-down notes and the stem-up notes like they are in the first image.

I've read the sections on beaming and edit mode, etc., but still can't figure this out. Any suggestions?