According to the document of Window type in QML:
"A Window can be declared inside an Item or inside another Window;"
However, the following code does not work with Qt 5.9.5 , Qt 5.10.1 and Qt 5.11 Beta 4 on Linux/Mac. The Window will not be visible.
However, the code above works with Qt 5.9.4 , Qt 5.10.0 . The window is visible.
This bug will affect multi-window applications, make it difficult manage multi-window object instance.
An example project is attached to reproduce the bug.