If a ticket in a ticket list is already opened by other Agent this is indicated in the list. A yellow vertical line symbol is shown first (left) in list. When you mouse over the line a popup is shown containing Name of Agent has opened the ticket.
Ticket already opened
Note: If user closes ticket correctly by selecting new Status or by x in the ticket tab is the indication automatically removed in other user´s view. However, if user logs out, close down or refresh browser or change language when a ticket is currently open, other users need to refresh Dashboard or View to remove the indication.
Note that if you disable Info Panels in User Profile, the already opened by popup is also disabled. Then only the yellow vertical line is displayed.