The extension sorts using directives in a special order.
Order is specified by:
For more details you can see the algorithm in the classes: LocationSorter, NamespaceSorter.
You can invoke the command from the context menu of the code window. Or you can set up invoking of the command automatically whenever document save (Tools/Options/Using Sorter). As you could note, the extension is written for Unity, but you can use it for any C# projects.