It would seem that in the design of QML user reparent was not really "envisioned", because even though it is possible, it involves creating and changing states, which is just not convenient to add to each and every item.
 import QtQuick 1.0
 Item {
     width: 200; height: 100
     Rectangle {
         id: redRect
         width: 100; height: 100
         color: "red"
     }
     Rectangle {
         id: blueRect
         x: redRect.width
         width: 50; height: 50
         color: "blue"
         states: State {
             name: "reparented"
             ParentChange { target: blueRect; parent: redRect; x: 10; y: 10 }
         }
         MouseArea { anchors.fill: parent; onClicked: blueRect.state = "reparented" }
     }
 }
I was wondering if there is a more elegant way to reparent items without polluting items with unnecessary states?