RailwayRouteOptimization/scripts/Modify/Offset/doc/Offset_proc_en.html

<ol>
  <li>Enter the distance of the concentric or parallel entity from the original
  entity in the options tool bar shown at the top.</li>
  <li>Enter the number of parallel or concentric entities to create in the
  options tool bar.</li>
  <li>Click the base entity. The parallel or concentric entities are created on
  that side on which the mouse cursor is located while selecting the
  entity.</li>
</ol>