These instructions relate to the legacy user management page in portals created prior to 2 April 2025 (AEDT).
No more need for a pesky .csv to add users in bulk to Groups!
Once a Group has been created, simply:
Navigate to the 'User Management' page under 'Administer'
Filter to your preferred users
Click the ellipsis (…) and select 'Add to Group'
Confirm your selection
Users are now added to the Group