Let’s see if this helps, Ian.
In SketchUp I set up dashes for the layer(s) associated with the components for which I’ll want to show hidden lines. I have two styles set up. One with Dashes turned off, the other with dashes turned on AND the Face Style set to Wireframe. Using the first style with Dashes turned off, I create a scene showing the components.
Then I choose the style with the dashes turned on, turn off layers I don’t need to see in the scene and create another scene with the same camera position.
When I send to LayOut, I set up a viewport showing the scene without the dashes. It goes on the lowest “model” layer. (My templates have between 3 and 6 model layers.) When I have the viewport scale set correctly and its position on the page established, I copy the viewport, make the next layer up the active one, right click in the main window and choose Paste to current layer from the Context menu. I immediately change the viewport to the dashed line scene. I end up with the illustration in the center of the page. I copied the viewports to the left to show each one individually.
You can adjust line weight and the dashes scale in the SketchUp Model panel to suit. Here’s a closer view of just the door.
Since these viewports are both still tied to their scenes, if I need to modify the hidden details such as add haunches to the tenons or make them through tenons, All I have to do is edit the components in the model, save the changes and update the reference.
A couple of important points to keep in mind. A layer for each viewport in the stack. Do not modify the scenes in LayOut (for numerous reasons). Simple Copy and Paste to current layer to keep everything aligned. Don’t move viewports around unless you move the entire stack. If for some reason you need to access a viewport down in the stack, lock the other layers and even turn off their visibility so you can easily get at the one you want.
I find this works quite well and it’s much easier to keep straight and much less work when the inevitable changes come along than manually created the dashed lines in LO.