Hi there,

I don't see there is a logic that Super User can approve users into the group as this should be done by the owner or admin of the group only.

For an example, this closed group is for the marketing only and there are many people requested to join. Super User does not know anything about marketing and the people who requested to join that marketing group BUT only the admin or owner of the group know the marketing and the requested people as they know them who is the one qualified into the group and who is not. So if Super User approves the people without the owner or admin's knowledge, this will be very not nice and there will be a privacy concern.

If you really want to do so, you can do it at the backend.