Hello again avs!
You'll be happy to know that we have some enhancements to user/group management in the Admin Panel coming this year. Your customer success manager can share more details with you.
In the meantime it's possible to update a user's group memberships in bulk with CSV import. This would only work for users not imported via AD or Azure directory sync (same goes for individual group updates from the Admin Panel).
Thanks for continuing to share your use cases with us. Feedback like this helps improve our product for everyone.