I create my index with makeindex, my .ist-file looks like that:
% sty.file for mkidx32.exe - redefines:
quote '+'
headings_flag 0
%headings_flag 1
heading_prefix "{\\textbf "
heading_suffix "}\\nopagebreak%\n \\indexspace\\nopagebreak%"
delim_0 ": "
delim_1 ": "
delim_2 ": "
%delim_r "~--~"
delim_r "-"
%delim_0 "\\dotfill "
%delim_1 "\\dotfill "
%delim_2 "\\dotfill "
%delim_r "~--~"
suffix_2p "\\,f."
suffix_3p "\\,ff."
The publishers guidelines say "no index letters", so I've set headings_flag to 0, which works as expected. But the guidelines also require the first letter of each first entry to be bold, like:
Aaaa Abc Adddd Affff
Bar Brrr Buuu
...and I have no idea how to realize that... any idea appreciated.
edit: Sorry, the MWE:
\documentclass[a4paper,fontsize=10pt,numbers=noenddot]{scrbook}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage[ngerman]{babel}
\usepackage{blindtext}
\usepackage[indentunit=0.75em]{idxlayout}
%\usepackage{makeidx}
\makeindex
\begin{document}
\blindtext\index{Aaronsen, John} Other names to be indexed are Mike Arjonen\index{Arjonen, Mike} and Jim Azzz\index{Azzz, Jim}. For B, there are John Baily\index{Baily, John} and Jim Bronson\index{Bronson, Jim}.
\printindex
\end{document}
And pls note I added:
\usepackage[indentunit=0.75em]{idxlayout}
for configuring the indention.
I also tried to set the first letter of each first entry bold manually (like \index{\textbf{A}aronsen, John}. Generally, this works, but I got a bigger line spacing after this first entry, which isn't an option...

*.istfile local on your system. the minute you turn in your*.texfiles, this won't work at all. – naphaneal Jun 15 '18 at 21:44heading_prefixvalue is incorrect. It should be to"\\textbf{"or"{\bfseries "`` not"{\\textbf ". I recommend you add a minimal working example (MWE) with a few indexed examples as people are more likely to answer questions if they can copy and paste a small but complete test document to work on. (Scroll down the to Index section of the MWE answer for examples.) – Nicola Talbot Jun 16 '18 at 12:11\documentclass[a4paper,fontsize=10pt,numbers=noenddot]{scrbook} \usepackage[T1]{fontenc} \usepackage[latin1]{inputenc} \usepackage[ngerman]{babel} \usepackage{makeidx} \makeindex \begin{document} text\index{Aaronsen, John} Other names to be indexed are Mike Arjonen\index{Arjonen, Mike} and Jim Azzz\index{Azzz, Jim}. For B, there are John Baily\index{Baily, John} and Jim Bronson\index{Bronson, Jim}. \printindex \end{document}– binsky Jun 16 '18 at 14:29"%tm.idx" -t "%tm.ilg" -o "%tm.ind" -l -s register.istregister.ist contains the code mentioned in original post.
In my original version, headings_flag was set to 1: https://www.screencast.com/t/z4IeahcOyIaJ
– binsky Jun 16 '18 at 14:39then I set headings_flag to 0:
https://www.screencast.com/t/G4srXdma much better, but in here the A of Aronson and the B of Baily should be bold...