You can File, Export to a O2C model and use the external viewer, but it won't dynamically update as you make changes. Sun Shader seems to block input to Datacad while open.
Thanks! - Josh Do. Or do not. There is no try. Josh's Digital Downloads is come back online soon. Stay tuned. (soon is a relative term)
....you could undock one of the viewer windows (ctrl - W) place it on your second monitor then set auto-update and a 3D view you want with Shade also turned on then it refreshes as you change the model and works using the Quickshade.
OK, it doesn't offer what you were looking for but will allow some level of 3D view update in a separate window and you can continue to update the window with each refresh as you design.