QML Tooltip visibility is set to false but should not

import QtQuick 2.12
import QtQuick.Controls 2.12
import QtQml 2.12

ApplicationWindow {
    visible: true
    width: 640
    height: 480
    Page{
        anchors.fill: parent
        ToolTip.visible: true // does not work, getting error : <Unknown File>:1:30: QML ToolTip: cannot find any window to open popup in.
        ToolTip.text: "Show something"
        Component.onCompleted: ToolTip.visible = true // workaround for line 13
        ToolTip.onVisibleChanged: {
            console.log("Global Tooltip is",ToolTip.visible)
        }

        Rectangle{
            anchors.fill: parent
            anchors.margins: 200
            color: "red"
            MouseArea{
                anchors.fill: parent
                hoverEnabled: true
                ToolTip.visible: containsMouse && false // is never visible, but when you hovering, the other Tooltip hides
                ToolTip.text: "You are hovering"
            }
        }
    }
}