When trying to perform a hit test using QAccessibleInterface::childAt() to find out which QQuickItem is at a given screen position, "unexpected" z orders are ignored. Usually the test returns the last declared sibling, instead of considering their z properties.

This can be tested when selecting accessible elements by tap on Android, or on iOS >= 18 when using my patch for QTBUG-140393.

import QtQuick
import QtQuick.Controls

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

    Button {
        id: hello
        text: "Hello"
        anchors.centerIn: parent
    }

    Button {
        text: "World"
        z: hello.z - 1
        anchors.centerIn: parent
    }
}

Here "World" will be selected, although it's visually below "Hello" due to the manually set "z" value.