AFAICT, all variables available to grantlee header theme editors are listed in https://invent.kde.org/pim/messagelib/-/blob/master/messageviewer/src/header/grantleeheaderformatter.cpp There, it seems some standard (although less common) headers are missing. Some of these are just variations of existing headers and so variables should be easy to create. Namely, not all Resent-* headers (https://datatracker.ietf.org/doc/html/rfc5322#section-3.6.6) are exposed to grantlee. Would it be possible to make Resent-Date, Resent-Sender, Resent-Cc, and Resent-Bcc available to grantlee for header themeing?