only after posting n reading ur post then i understand in the xml there are 2 set of objects drawing in the v-t graph.
[b][color=blue]this is important quote"You can only drag an object when it is visible. "[/color][/b]

one is the set of ParticleSet_movable2 | visible mode.equals("edit_v-t_graph") | OnDrag dragvt();
dsnap(); |
other one  is the Polygon_line_during_edit_options | visible mode.equals("edit_v-t_graph") | OnDrag dragvt();

what i did that i think achieve what i want is to create another object called Polygon_line_for_non_edit_options | mode.equals("simple_acceleration")||mode.equals("uniform_motion")||mode.equals("simple_deceleration")||mode.equals("rise_and_fall")||mode.equals("fall_and_rebounce") |  [color=red][font=Verdana]DragOn  "BLANK" !!!! [/font][/color]

done!!!

yes you r right, i will try to rearrange the simulation vertical from current horizontal ASAP :)

Thanks!