There has been some discussion about the best way to handle door thresholds and the Cadimage settings. There is a toggle for a threshold, but it does not affect the 3d view... unless you give it a dimension.
This is not a toggle to turn on or off the threshold, but rather extends the jamb element across the base of the door opening for a given thickness. There is apparently no way to apply a sill or threshold object, with a given profile, but if you need a 3d element to show a stand off height for the base of the door in plan, section and elevation this is how you do it.
If you need the threshold or sill plate to be a material other than your door frame, or need a specific profile, then the solution will have to be a custom beam, slab, morph or object set into the door opening and not linked to the door component.