Cannot create a binding to the user defined property

I created a property in .ui.qml, using "Properties" like this.

What I wanted to do is like this:

ItemBuffer {
    id: root
    property bool show: false
    property real showAnimator: show ? 1 : 0 // <=== This is what I wanted to do 

But in the "Bindings," I cannot find the property I created, in this case, "showAnimator," in the "Property."