Draw Select replicates the Mode, Line Type and Scale of a source Extension.
Extension Lines placed with the Single Extension command will pull from the closest extendable location rather than use the System/Project/Drawing setting.
This applies to extendable objects including Openings, Shapes, Solids and Posts.
This makes it easy to pull an extension from the center of a window and the edge of a garage door without having to change and change back the extension location configuration.
Extensions will not pull from Shape Splines or Solid 3D Splines.
Extensions do a better job of remaining attached to wall materials as the walls move in and out of wall joins.