In macOS it’s possible to change the order of icons in the menu bar via Command-drag (hold down the Command key and drag the item to the desired position).
If you want to save some space in your menu bar you can also turn off the menu bar icon of Little Snitch completely. Options like choosing the operation mode or selecting profiles are then still accessible in the Settings window of the Little Snitch app, and the Network Monitor window can still be opened via a configurable keyboard shortcut.