Hello Andy,
You can definitely customize the dashed line style appearance. To do so, I would recommend crating a custom drawing set via the Configurator, and saving it for your project. One easy way would be to open up the standard “ConDoc v4 – ARCHITECT.condoc” drawing set, and make a note of the layers/styles that are applied to the viewport scenes. For example, if you’re using the ‘Construction Plan’ as the drawing you want to adjust the hidden line style, take a look at default settings applied; you can easily create a new viewport and call it ‘Custom Dashed’, save that set as your own modified .condoc drawing set and give it a shot.