Event.command

説明

「 Command/Windows 」キーが押されたかどうか（読み取り専用）

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;

public class Example : MonoBehaviour
{
    // Prints Command/Windows key was pressed depending the
    // platform this script is being run.
    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!");
            }
        }
    }
}