Instantiate prefabs before runtime, inside editor

Hello! How do I instantiate prefabs so I can interract with them in the editor, without the game running? Instantiating prefabs is not the problem, but to do it once to create a map for the editor is what I need some help with.

I have searched for this online without any good results, so hopefully someone here knows a good way to do this :)

Thanks in advance.

EDIT

I know that I can simply drag a prefab to my editor. Say I want a 10x10x10 cube made up from smaller same-sized cubes. Instead of dragging in 1000 prefabs att an exact location, I want to add them from script, something like this:

 for(int i1=0;i1<10;i++){
    for(int i2=0;i2<10;i2++){
       for(int i3=0;i3<10;i3++){
           InstantiateIntoEditorBeforeRuntime(Resources.Load("myPrefab"), Vector3(i1,i2,i3));
       }
    }
 }

(something like that)