Let me come back to the unresolved (for me) question of two situations in sub entries to a book index (register). Sub entries that have formatting or sub entries that are surrounded by quote marks (straight or curly, it makes no difference) do not appear in the correct alphabetical order.

Two attempts on my part:

text before \index[Plenary+periti]{Plenary Council+{\it periti} (experts)} text after.

text before \index{animals+‘special kinds’} text after. Or alternatively, \index[animals+special]{animals+‘special kinds’}

The setup for my register is a pretty standard one. The processor is not for the 'periti' case above but I use it for book titles.

\setupregister[index][n=1,method={zc,pc,zm,pm,uc},style=WORD]

\defineprocessor[special][style=italic]

In the periti case it is the \it command that clearly interferes with correct alphabetic positioning in the sub entry list. Placing +periti in the key does not overcome that problem.

In the ‘special kinds’ case it is the initial single quote mark (‘) that causes the problem. The item comes last in the sub entry list. And if i include a key [special], then it comes first in the sub entry list. Either way, it is out of the desired sorting order.

I believe I have followed the helpful suggestions of various ones, but it is always possible that I have not fully understood those suggestions. The reality is that at the moment the issue remains unresolved for me. Any further wisdom out there to offer me?

Julian