Place the main stack where you want to put the marker. After choosing the marker type (Button, Icon or Image), give it a unique name. Give the same name to the child-stack and "tear" it off, positioning it at the scroll target.
Documentation
General Settings
Scroll Target ID - this is the unique name for a particular instance of the Scroll To stack. Make sure to assign the same name to the child stack. Avoid blanks and complicated names
Alignment - to align the marker, use the "left", "center", "right" options
Specific Settings
Easing - choose from the 10 available easing effects
Duration - specify the duration of the selected easing effect
Offset - specifies the offset (from top) of the scroll position, e.g. to avoid the height of a fixed menu bar