@jpnurmi
Well, I found a temporary solution while the original idea is fixed with dragMargin. Making the width is 0 can disable the Drawer, but only with the combination of width and dragMargin, if only use width, is still possible show a Drawer (an empty drawer)
Drawer {
dragMargin: appContentManager.depth > 1 ? 0 : Qt.styleHints.startDragDistance
width: appContentManager.depth > 1 ? 0 : Math.min(appRoot.width, appRoot.height) / 3 * 2
}
I also report the bug
https://bugreports.qt.io/browse/QTBUG-54629