Thank you Franz. I did use the work "override" -- but I didn't mean that in the sense of C++ virtual methods. I'm not attempting to redefine QGraphicsItem::setToolTip() in any of my classes.

I just want the child QGraphicsItem's "setToolTip" call to PREVAIL over the containing (parent's) "setToolTip" call when the mouse pointer is over the child QGraphicsItem.

I did also make sure that the child QGraphicsItem had a higher "Z" value than the parent QGraphicsItem -- that didn't help. Only the tooltip text set by the parent's setToolTip call ever shows up.