How to add existing users as group admin?

Is it possible for group administrators to add existing users to their own group? If yes, how?

Example: A user already exists in group A, but not in group B. The group admin of group B wants to add this user to his group. However, only users already in group B are visible for the group admin.

Nextcloud version: 14.0.3

Did you have restriction that users can only see users within their group when sharing (on the admin page)? Or auto-completion for user names turned off?

No and no. Would that make a difference?

Any news here?

I have the exact same issue.

Nextcloud Version: 15.0.4

Hi, any support would be appreciated very much. Input please?
Running NC 17

Still an open question for nc20.