Access Sorted Index in FormRepeat

Hello,
I need the index of the form-repeat items after reordering them via the “sortable” option by drag and drop. As you can see below, I display the $index of the item as a Heading using a Dynamic Attribute binding, but after reordering them, the index doesn’t change, even though the order the items are displayed in has changed. How do I access the index of the order they are displayed in?

Dynamic Value Binding the index of the FormRepeat:

Index display before reordering:

Index display after reordering with “sortable” using drag&drop: