Thanks for considering this @chris !
I am willing to test this implementation if you want, I can run inter-software validations (e. g. compare LBT with DesignBuilder) for various glazing buildups.
This capability becomes very important when caclulating transmitted solar radiation through IGUs with selective coatings, which are typical nowadays. I have previously compared results between broadband and spectrally defined glasses, and broadband always underestimate transmitted solar significantly. This is why it would be very useful to be able to assign the properties (reflectance, transmittance) with the E+ Optical Data Type=Spectral, not SpectralAverage.