Unsolved source item to be glowing on popup modal set

[dsba]

Hi All,
I was working on pop-ups, on set of modal to true, whole window goes dim, whereas I wanted the pressed button/source item to be glowing. Below is the sample code.
I am trying set property z of testButton so that it appears on modal dim effect. Kindly help me out to understand what I have missed.

Thanks in advance,

import QtQuick 2.12
import QtQuick.Window 2.12
import QtQuick.Controls 2.12
import QtGraphicalEffects 1.0

Window {
id: root
visible: true
width: 640
height: 480
title: qsTr("Hello World")
color: "pink"

Button {
    id: testButton
    x: root.width/2 - testButton.width/2
    width: 70
    height: 116
    z: 0
    background: Rectangle {
        color: "white"
    }
    text: "B1"
}
MouseArea {
    id: testButtonMouseArea
    anchors.fill: testButton
    onClicked: {
        testButtonPopUp.open()
    }
}


Popup {
    id: testButtonPopUp
    width: 200
    height: 300
    modal: true
    onOpened: popUpBackRect.state = "on"
    onClosed: popUpBackRect.state = "off"

    background: Rectangle {
        id: popUpBackRect
        color: "white"
        states: [
            State {
                name: "on"
                PropertyChanges { target: testButtonPopUp; dim: true; }

// PropertyChanges { target: testButton; z: 2 }
},
State {
name: "off"
PropertyChanges { target: testButtonPopUp; dim: false; }
// PropertyChanges { target: testButton; z: 1 }
}
]
}
}
}