unity set parent canvas
[MenuItem("GameObject/UI/Switch")]
static void Switch()
{
//Create new GameObject
GameObject go = new GameObject("switch");
//Find Canvas in the Scene
Canvas canvas = (Canvas)GameObject.FindObjectOfType(typeof(Canvas));
//Get Canvas GameObject
GameObject canvasGameObject = canvas.gameObject;
//Make the new GameObject child of the Canvas
go.transform.parent = canvasGameObject.transform;
go.transform.localPosition = Vector3.zero;
//Change the new GameObject Layer to UI
go.layer = 5; //Or go.layer = canvasGameObject.layer;
//Add Rect Transform to it
go.AddComponent<RectTransform>();
}