Undo.SetTransformParent

public static void SetTransformParent(Transform transform, Transform newParent, string name);

Parameters

transform		The Transform component whose parent is to be changed.
newParent		The parent Transform to be assigned.
name		The name of this action, to be stored in the Undo history buffer.

Sets the parent of transform to the new parent and records an undo operation.

This is equivalent to calling transform.parent = newParent, but it additionally records the undo operation.