Unfortunately I cannot help with the questions regarding LBNL WINDOWS. I have only generated BSDFs once some years ago, otherwise I have used genBSDF as Chris linked to above.
I guess you do not need the glazing, necessarily. If you have a BSDF of just the perforated material, you can model the venetian blind slats in Rhino/Grasshopper and add the BSDF modifier to that geometry. But I am not sure how well this will work if the slats are in any way curved. This way your BSDF is not dependent on the glazing (visual transmittance) or the slat angle of the venetian blinds. So you can simulate different glazings and slat angles using just one BSDF.
Or you can model the exact venetian blind geometry in a closed state with perforation and create a BSDF material for that. For this you will probably need genBSDF. You can then create a face (the incident side of the venetian blinds) in Rhino/Grasshopper and add the BSDF modifier, and probably set a thickness to the modifier.