On the same staff, can I not beam 8th notes of the top AND bottom voice? Every time I try to group them, the beams of one voice are replaced with individual 8th notes.
You have to use Staff Layering to do this. Look for this feature in the Help, or search this forum.
See https://forum.noteworthycomposer.com/?topic=152, https://forum.noteworthycomposer.com/?topic=870