Event.command

설명

Is Command/Windows key held down? (Read Only)

On Windows, this returns true if any Windows key is held down.
On Mac, this returns true if any Command key is held down.

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void OnGUI() {
        Event e = Event.current;
        if (e.command)
            if (Application.platform == RuntimePlatform.OSXEditor)
                Debug.Log("Command key was pressed");
            else
                if (Application.platform == RuntimePlatform.WindowsEditor)
                    Debug.Log("Windows Key was pressed!");
                
        
    }
}