REG: Material elevation in Page header

import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Controls.Material 2.2

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    title: qsTr("Tabs")

    Component {
        id: comp
        Page {
            header: Pane {
                Material.elevation: 6
                height: 200
            }
        }
    }

    StackView {
        id: stackView
        anchors.fill: parent
        initialItem: comp
    }

    MouseArea {
        anchors.fill: parent
        onClicked: stackView.push(comp)
    }
}