For Service Portal you need to configure the standard ticket page, by default there are two tabs Activity and Attachment, you can delete Activity tab or change it to some other options like associate request etc.
In the navigation search type "Standard Ticket Configuration" and select the respective tasks like Incident or Change or Request. Incident you will find two tabs Activity and Attachment. If you need to hide Worknotes or activity for all users in Service Portal including ITIL user then you can delete the Activity tab in this configuration or deactivate the OOB configuration and create new configuration by default it will have Activity and Attachment associated with the page configuration, delete the Activity tab.
After deleting activity tab from the Standard Ticket Configuration for incident. Only attachment is visible and activity is removed. Like this you add or remove or change the existing tabs with available and add custom tabs and widgets.
Before deleting the tab
After deleting tab
You can also try the advance configurations, through scripts you can set visibility for the tabs in the portal incident view.
Revert if you have any questions. If my response helps to solve your issue. Kindly mark it as helpful & correct.
When I delete that activity, all work notes and User communication are disappearing. But i want only work notes should be hide all users.
When i wrote the below script, i am getting the below error. Please check
