I'm able to export to CSV via 0365 exchange gui, but the CSV file it creates only lists the names of the nested groups themselves, not the users within.
I worked around this by simply exporting the nested groups direct to two seperate CSV files (via Powershell) then combining the two. The area where I'm confused is exporting the "identity" information so that importing is simple. I ended up with email addresses, alias, etc. etc. but scripts I found all mentioned specifically "identity" as the key to importing the users into a newly created distro group.
Thanks in advance for any help.