Here at Talkdesk, we're aware that our customers' operations may have specific needs when it comes to Callbar using. So, if there is a need to restrict access to Callbar to certain Agents, you can do this by setting different Roles and setting up their Role restrictions.
Each user's Role is defined when they are added to your Zendesk, but you can change a user's Role as needed. When users sign in, they are only shown the parts of your Zendesk that they are allowed to see and use.
To set up the different Role restrictions in Zendesk, go to Admin > Apps > Manage > Change your role restrictions: