Because the grantor letter contains detail, not summary, numbers, the export of the grantor information would require entirely different programming than the currently-existing export of the K-1 summary numbers. 

There is more than one way to skin this cat. On the 1040, enter the grantor trust items directly, as the first input you do on the return. Print the output detail pages (Sch B, Sch E, whatever) to PDF. Attach them to the 1041 e-file as the grantor detail. Continue to bill the attorney for the consequences of their poor life choices, because this time savings was due entirely to your own cleverness, not to any improvement of their life choices.