The group administrator can export the member list both in the app and on web. You can only do this from the main group but the export will include all sub groups on separate tabs.
In the app
Enter the main group and press the members tab
Press the Excel icon in the top right corner and Export member list to Excel
Chose which way you would like to send the export
Enter the main group and press the three dots to the right next to '+ create subgroup'
Select Download member list (Excel)
The export will save to your download folder on your computer
The export includes numerous pages:
An overview over all members, their guardians and all member fields
A print friendly version
Each sub group separately