According to http://wiki.contextgarden.net/Registers#Processors, processors are the MkIV way of highlighting within index entries.
If there are highlighted and not-highlighted entries, the normal version wins. If there is a highlighted version with subentry, the subentry becomes highlighted and is sorted unter the normal main entry, if there doesn’t exist a normal entry with the same subentry. (These are just observations, I wouldn’t know how it should be different.) But: Is there a way to highlight just subentries? e.g. \index{Sun+emph->rays} """ \defineprocessor[emph][style=italic] \starttext \index{Sun} \index{Sun->rays} \index{emph->Sun} \index{Sun+emph->rays} % doesn’t work \index{emph->Sun+rays} % rays upright \index{emph->Sun+beams} % beams italic \placeindex[n=1] \stoptext """ Greetlings, Hraban --- https://www.fiee.net http://wiki.contextgarden.net https://www.dreiviertelhaus.de GPG Key ID 1C9B22FD ___________________________________________________________________________________ If your question is of interest to others as well, please add an entry to the Wiki! maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context webpage : http://www.pragma-ade.nl / http://context.aanhet.net archive : https://bitbucket.org/phg/context-mirror/commits/ wiki : http://contextgarden.net ___________________________________________________________________________________