Use the Business User tab to set access rights on request tickets for the client.
Navigate to Setup > Service Desk > Settings.
Select the Business User tab.
The following Property settings are mutually exclusive and work independently.
To grant a user permission to only view the list of tickets, set Give the read only access to the requests to ON:
The user cannot open tickets to get more detailed information.
To grant a user permission to view ticket details, set Allow only update comment to the request to ON:
With this permission, the user is restricted to being able to update the conversation, only.
Click Update to apply the settings.