Hey Christian,

First, note that the Abbe number is a very specific characterization of the slope of the dispersion curve; by definition it is measured at the FdC spectrum & represents a “pivot” of the dispersion curve around the d-wavelength.  The following article goes into more detail about how OpticStudio models TABB:

(25) Modeling Refractive Index | LinkedIn

Since TABB uses a material solve and the wavelengths for a Material Solve are between 300nm to 2500nm, you can still use TABB directly in your tolerancing.  I would suggest downloading the ZAR from the above article, change the material on Surface 1 & Surface 3, change the vd offset on Surface 3, & then refresh all the windows.  You will be able to see the difference between the nominal index (blue) and the toleranced Abbe (green) at the desired wavelengths between 950nm-1800nm.  Once you find your extreme FdC Abbe numbers that reflect your expected dispersion curve, you can enter these directly into the TDE.

Note that if you need to model refractive index tolerance outside of 300nm-2500nm, then you will have to model the change in dispersion (both y-intercept and slope) outside of OpticStudio by manually modifying an AGF glass catalog and then using this modified AGF catalog in your tolerancing.