The new case viewing notification feature is currently enabled on all support cases. This means that when you click on a case in your queue, you can see if anyone else is viewing the case at the same time by looking at the Other Record Viewers box here.

When other users open this case, their names will populate within this box. Please note that if they have the case open in multiple tabs their name may populate multiple times and this is normal. If another user navigates away from this case, you can refresh the page to see that their name no longer appears in this box.