Shortcut that starts from a StandardKey but requires an extra modifier?

[pokemonsrqt]

The first two actions work nicely. But the last two action don't. I'm not completely sure why.

Action {
    id: zoomInOnXAxis
    text: qsTr("Zoom In On X-Axis")
    shortcut: StandardKey.ZoomIn
    onTriggered: console.log("Zoom In On X-Axis")
}

Action {
    id: zoomOutOnXAxis
    text: qsTr("Zoom Out On X-Axis")
    shortcut: StandardKey.ZoomOut
    onTriggered: console.log("Zoom Out On X-Axis")
}

Action {
    id: zoomInOnYAxis
    text: qsTr("Zoom In On Y-Axis")
    shortcut: qsTr("Ctrl+Alt+Plus")
    onTriggered: console.log("Zoom In On Y-Axis")
}

Action {
    id: zoomOutOnYAxis
    text: qsTr("Zoom Out On Y-Axis")
    shortcut: qsTr("Ctrl+Alt+Minus")
    onTriggered: console.log("Zoom Out On Y-Axis")
}

How can I get them to work? Is it perhaps possible to define a shortcut that is something along the lines of StandardKey.ZoomIn+Alt?