Oh ok, now I understand your issue.
Try this - remove ScrollTo behavior, set Unbounded scrolling=Yes in layout properties and add this event:
System -> Every tick
........System-Set scroll X to clamp(Player.x, OriginalWindowWidth/2-50, LayoutWidth-OriginalWindowWidth/2+50)
........System-Set scroll Y to clamp(Player.y, OriginalWindowHeight/2-30, LayoutHeight-OriginalWindowHeight/2+30)
Where 30 and 50 is the thickness of your HUD borders.
This will allow to scroll the layout 30 and 50 pixels beyond the layout size.
OddConfection You beat me by just 1 minute!