Edit a inspector variable from editor script.(its not saving)

I need to give my objects of a same parent class a different ID. I wrote a editor script to do this and that works.

But when I save and load the scene, the ID have their default values again.

The parent class that hold the ID:

 public class SavableClass extends MonoBehaviour
 {
     public var uniqueSaveID : int;
 }    

The editor script:

 public class SaveIDsManager extends ScriptableWizard
 {
     new function OnGUI() :void
     {
         if(GUILayout.Button("Set Save ID's")) 
         {
             SetIDs();
         }
     }
     
     function SetIDs() :void
     {
         var SavableClasses     : SavableClass[]    = FindObjectsOfType ( SavableClass );
         
         for ( var saveScript : SavableClass in SavableClasses )
         {                
             // If no ID
             if ( !saveScript.uniqueSaveID )
             {
                 saveScript.uniqueSaveID = FindFreeID();
             }
         }
         
         function SetIDs() :int
         {
             // code checking what id is next
             var availebleID : int = 10;
             return availebleID;
         }
     }
 }