🚀 go-pugleaf

Hello Violaine,
Bill's advice is good but might appear to a new user as a big thing to do. It's really only a few minutes work if you have an index file in another book that looks just like you want for your new index. The steps are:
1. Delete the bad index from your book
2. Add a new index file using the book tools and regenerate the book.
3. Open your good looking index and import formats from this to your newly generated index.
4. Regenerate your book to apply the formatting.

It will took less than 5 minutes and is general practice anyway for a new book.

If your not comfortable with this get a copy of Adobe's Classroom in a book and read Lesson 12. Lesson 12 also has several good tips about solving Index formatting problems like split page numbers, getting page ranges, and removing page numbers from cross referenced index entries.
Cheers
Ian