What tripped me up when I did some QML is that interop of lists between C++ and QML is usually shown in tutorials as going via QQmlListProperty but that is actually not what it's supposed to be used for, resulting in subtle memory leaks and crashes when ownership gets mixed up.

Additionally, it only JUST got a TreeView (Qt 5.5 I believe) and a lot of additional widgets you would need to implement a regular desktop app are just missing.