This is a requirement for scenarios like below: The Dashboard may be configured differently and personalized by a user. A support representative will require a way to see the user's current customization (like Dashboard , pages etc) in order to help with trouble shooting. The support representative who will be having an admin role, should get to see the customization without logging as the non-admin user.
Related GateIn documentation: https://docs.jboss.org/author/display/GTNPORTAL38/Impersonation
Documentation for additional permission "user.impersonate.groups" related to this feature: https://docs.jboss.org/author/display/GTNPORTAL38/Portal+Default+Permission+Configuration
Verified in ER01