To grant a delegated admin the group reference right:

  • Run dsconfig with the create-delegated-admin-resource-rights option. 
    dsconfig create-delegated-admin-resource-rights \
    --rights-name DArights  \
    --rest-resource-type groups  \
    --set enabled:true  \
    --set admin-permission:reference  \
    --set admin-scope:all-resources-in-base
The admin can see the user's group memberships on the entry preview's Group Membership tab.