From this previous post by me Viewport Class Overrides and the like If you allow a hook into the line type and pen thicknesses at least, it would save us heaps of hours having to select a viewport and pain-stakingly scroll through 100's of classes to find the one your looking for and override it. Also using the eyedropper for VP class overrides and visibilities is ok until you have two viewports that you want to eyedropper a single class' properties across without carrying prope