Properties View: Make "Custom Properties" editable from the parent's editor

// MyWidget.ui.qml
import QtQuick
import QtQuick.Controls.Basic

Item {
    width: 200
    height: 100

    property alias myRectangle: myRectangle
    property alias myButton: myButton
    property alias myItem: myItem

    Rectangle {
        id: myRectangle
        color: "green"
        property string description: "A Rectangle"
    }

    Button {
        id: myButton
        checkable: true
        property string description: "A Button"
    }

    Item {
        id: myItem
        property string description: "An Item"
    }
}

// MyScreen.ui.qml
import QtQuick

Rectangle {
    width: 640
    height: 480

    MyWidget {
        id: widget
    }
}