Konstantin1
That's confusing as the setting you mentioned from v1.7 has nothing to do with this.
Anyways, you can go to any Agent under Admin Panel > Agents > Agents > click the Agent, click the Permissions tab, deselect the option for Agent - Ability to see Agents in all Departments.
, and Save Changes. Now this Agent will only be able to see the Agents in the Departments they have access to.
Cheers.