The FlowchartX scrollbars are the builtin scrollbars that the Win32 API creates when you call the CreateWindow(WS_HSCROLL | WS_VSCROLL) method. Check if the skin framework has some property that enables processing of such scrollbars.

Otherwise you could call the HideScrollbars method to hide the builtin scrollbars and add separate ones aligned to the right and bottom of the flowchart canvas. You will only have to set the flowchart's scroll position in response to the scrollbars events, and update the scrollbar ranges after resizing the flowchart with methods such as SetDocSize and FitDocToItems.

I hope that helps,
Stoyan