Comment 1 for bug 1389711

ToolbarItems can contain any Items, which will go in the toolbar. But with the new header, the toolbar (and ToolbarItems) are deprecated and you should use the new API: http://developer.ubuntu.com/api/qml/sdk-14.10/Ubuntu.Components.PageHeadConfiguration/

Whens switching on the new header (MainView.useDeprecatedToolbar: false), the ToolbarButtons of the ToolbarItems are indeed automatically put in the header, but this is only to provide some temporary backwards compatibility to use old code with the new header. Apps should switch to using Page.head instead, which also gives them access to new functionality.

What needs to happen here is that ToolbarItems must be marked as deprecated.