In the support ticketing extension, By default tickets of a specific department are visible to only members of that department.

How can I make all tickets of all departments visible to all users?

This can be done from the configuration panel. Just follow the below steps

1. Go to Support/Helpdesk
2. Click on "Go to Admin panel"
3. Click on "Staff"
4. Click on "Usergroups"
5. Select the user group "Staff" and select all the departments u wish to give access to