Please check the help menu of the demo app of the latest TSimpleraph.
I am pasting some tips:
DRAG LINK If the link does not have any fixed point, moves the link.
DRAG POINT If the point is not fixed, moves the point. If the point is an endpoint, and ALT key is not down, dropping the point on an object establishes a link.
ALT+CLICK POINT If the point is not fixed, removes the point.
ALT+CLICK LINE If the link is not marked as fixed, inserts a new breakpoint at the clicked coordinates.
RIGHT+CLICK If a point is dragged, inserts a new breakpoint. The source point of the drag action, keeps its dragging state.
check the source of the demo app - it's easy