Hi Chipp - transparency for surfaces hasn't been a priority yet because of the hidden line view (View > "Display hidden lines" checkbox) which when enabled already lets you get an idea of the structure of hidden objects and also allow you to select edges and curves.

It is also possible to set objects into "faint wireframe" mode where the surfaces are hidden and the edges are displayed in a dashed style, that's what Pilou shows above.

I would like to add in an actual transparent surface mode in the future but it's hard to say when it will be implemented, because there is far more work to do to make it happen than just modifying a transparency value. In order to do a transparent display requires a lot of special attention to the draw order of polygons in the display engine, they have to be drawn in back to front order in order for the opacity to work correctly. That sorting can tend to incur a high performance cost and so it's something that has to be implemented with a lot of care, making it a fairly time intensive feature to add.

- Michael