How to use Forced grabbing

You can use ForceSelect():

// Force Select on trigger enter
private void OnTriggerEnter(Collider other)
    {
        Debug.Log("triggered: " + other.name);
        // modify GetComponent scope on line below as you need
        var handGrabInteractor = other.GetComponentInParent<HandGrabInteractor>(); 
        if (handGrabInteractor == null) return;
        handGrabInteractor.ForceSelect(handGrabInteractable);
    }

 To release you can use ForceRelease()