You can group work items in the Service Matrix by creating higher-level Process Groups into which you can nest multiple Cases/Tickets.
In order to create a Process Group, go to the Service Lines screen and then in the Case or Ticket you want to add to the group, define the name of the Process group:
When you switch over to the Service Matrix Screen, you will be able to see that your Cases and Tickets are now grouped. Clicking on a Process Group tab will reveal the Cases / Tickets within that Group.
Note that the 2 letter abbreviation for the group will come from the first two letters of the group name if the Process Group name is one word (e.g. International will be abbreviated to IN) or from the first letter of the first word and first letter or the last word if the group name is more than one word (e.g. HR International will be abbreviated to HI).
A setting in General Setting lets you decide if you want to show or hide process group information in both Builder and Work Manager.
If the setting is off, all process group labels and fields will be hidden.
Note that if a user tries to switch off the option after having added process group information, they will not be able to switch it off.