ok I use Flowstone 3.0.8 Skylark
in module Pad Control
you need to create links from Xmin (=0), Xmax, Xset, Ymin (=0), Ymax, Yset, and dragging(primitive drgXY) to a new module named 'default to center'
The connections are a bit fuzzi but i did it quick en dirty.
PadControl.png
In new module ...

Is this what you are looking for?
I modified the pad control : returns to default center position when dragging stops.