Adding Section Heads in an InDesign Index with GREP

If you ever have to add section letters to an existing index in InDesign, you can do that quickly using a GREP query. 

You use a single query: Find what: ^(\u).+\r(\1.+\r)+ and Change to: $1\r$0. Translation: match and capture a capital ((\u)) at the beginning of a paragraph (^), and then match all following characters in the paragraph (.+) up to and including the return character (\r). Then match a letter that’s the same (\1) as the one we captured earlier, followed by all characters up to the end of that paragraph (.+\r), group that, and find as many as possible of the same (+). In the example above, ^(\u).+\r matches Barbera 14 (and the return character), and (\1.+\r)+ matches all following lines that start with B. And there’s your section. 

Now, to insert the section letter (which is the letter we matched by ^(\u)), we replace the section with the letter we captured ($1) followed by a return (\r) and the entire section ($0)—remember that $0 stands for “everything that was matched by the Find What expression.”

If you want to apply a paragraph style to the section letters, e.g., to add some space before and a font style, that has to be done using a very simple, separate query. At Find What, enter ^\u$, and in the Change format panel, enter the paragraph style—in other words, apply a paragraph style to all one-letter paragraphs. Make sure the Change To field is empty, and then click Change All.

The drawback of this method is that it makes a mess of any formatting, such as italics. You can convert formatted text to text tags, insert the section letters, and then convert the text tags back to the formatting.