Right now QQC2 menus are drawn as child items of their parent windows, and are not separate windows. This causes a variety of issues of menus not appearing in the right place, being cut off when the parent window is small or positioned mostly off-screen, etc. This is ultimately a Qt issue (see https://bugreports.qt.io/browse/QTBUG-69558), but we should investigate fixing this in our theming to make menus spawn a separate window.
*** Bug 458183 has been marked as a duplicate of this bug. ***
*** Bug 452956 has been marked as a duplicate of this bug. ***
*** Bug 456893 has been marked as a duplicate of this bug. ***
*** Bug 447334 has been marked as a duplicate of this bug. ***