Navigate to the upper left of your main screen and left click to bring up the Time Zone quick menu

Click to Add Time Zone to open the manager

Choose the Time Zones you’d like access to from the quick menu by either double clicking or utilizing the arrows to move them over

Going back into the quick menu we can see the 3 added Time Zones

You can have 1 additional Time Zone active from the quick menu

Hover over each Time Zone to edit or reset a custom name that will appear alongside the current displayed time of that Time Zone and even remove entirely from the quick menu