well, there is no API to do this as not many users have requested it.
however, you could modify NetAnim by changing resizeableitem.cpp
to show like this
case ResizeableItem::CIRCLE:
{
painter->drawEllipse (QPointF (0, 0), m_width * 2, m_height * 2); // sensing range circle with radius == 2X node radius
QBrush brush;
brush.setStyle (Qt::SolidPattern);
brush.setColor (QColor (m_r, m_g, m_b, m_alpha));
painter->setBrush (brush);
painter->drawEllipse (QPointF (0, 0), m_width, m_height);
}
gives the attached picture
AnimNode, inherits from ResizeableItem and only animnode stores the nodeid, so you need to store a mapping of nodeId to sensing range in Resizeableitem.