just implement the GlobalConfig in following ways

property QtObject gConfig: GlobalConfig {}

and than

property Gradient offGradient:		gConfig.offlineGradient

it works

Normally that works but i have not so much elements.
My Element is a Button and it is just a Rectangle with some variables and a mouse area. This button i use as component in other qmls. And now to add additional Items for a workaround i don't want, because i think it is not a "nice" solutions, i hoped that i found a more correct way to "copy" just the value from a property to a new property.
My actual workaround is to have local propertys and no link to my globalconfig.

Window {
    width: 200
    height: 200
    visible: true

    property int globalProperty: 30

    Item {
        id: item
        property int localProperty: globalProperty
        anchors.fill: parent

        Text {
            id: txt
            anchors.centerIn: parent
            text: item.localProperty

            MouseArea {
                anchors.fill: parent
                onClicked: {
                    item.localProperty = 60
                    console.log(globalProperty)
                }
            }
        }
    }
}

Initially localproperty holds the globalperoperty. Then on click just changes the localproperty and not global one.

That is the way i'm looking for. but how to do?

property Gradient offGradient: Config.offlineGradient

That is the way i did. I have different gradients for different states.
Later i modify the actual gradient with

Qt.darker  
Qt.lighter

for some mouse-actions (hover, clicked etc.)

So at the moment i have the problem that my globalConfig.offlineGradient get the change and not just offGradient.