why doesn't the glass in my doors show as transparent when the windows do?

[Cadplan Architecture]

I have used the bi fold doors plug in from the VW 2008 object library, and also imported windows from the same source.

The default door leaves are solid but I have found out now how to make them glass with solid frames. The glass just shows as clear though when rendered not like the glass in the windows and I can't see any control for the glass under Settings. I actually tried ungrouping the doors and the glass is not a solid it's wireframe which I guess is the problem. The question is- Can I ungroup then edit and then assemble all the parts again into a symbol/plug in or whatever it started as, so that it will click back into the wall?

Also I want only 3 folding door leaves but the option only seems to be for 4. AJ