Someone

void BoxLayout::insertItem(int index, QGraphicsLayoutItem *item)
{
    if (!item || d->children.contains(item)) {
        return;
    }

//     item->setManagingLayout(this);

    if (index == -1) {
        index = d->children.size();
    }

    d->children.insert(index, item);

    if (animator())  {
        animator()->setCurrentState(item, LayoutAnimator::InsertedState);
    }

    updateGeometry();
}