The Clocks palette can list clocks horizontally or vertically.
On macOS 13 or later, choose World Clock Deluxe > Settings. On macOS 12 or earlier, choose World Clock Deluxe > Preferences. Click Palette and select or deselect the "Display clocks vertically" checkbox.
Control-click the palette's background and choose Display Clocks Horizontally or Display Clocks Vertically from the shortcut menu.
Shift-Command-click the palette's background.