For mesh tracking instantiate XRReferenceObjectLibrary instead of loading it from resources

    {

        XROrigin origin = UnityEngine.Object.FindAnyObjectByType<XROrigin>();

        m_trackedObjectManager = origin.gameObject.AddComponent<ARTrackedObjectManager>();

        XRReferenceObjectLibrary library = (XRReferenceObjectLibrary) Resources.Load("ARFObjectLibrary");

        XRReferenceObjectLibrary library = (XRReferenceObjectLibrary) ScriptableObject.CreateInstance(typeof(XRReferenceObjectLibrary));

        m_trackedObjectManager.referenceLibrary = library ;

        m_trackedMeshesInLibrary = new List<string>();

        m_trackedObjectManager.trackedObjectPrefab = (GameObject)Resources.Load("ARFMeshTrackingPrefab");