How can I export only text with a distinctive character style from InDesign to a new document?

Here’s a method that works and doesn’t require anything other than basic InDesign features.

It’s pretty easy, but has a few steps, so, if you need to do this often, it might be worth looking into using scripts instead (see comments below) so you can do all of this with one click, not many.

1: In a copy of the file, remove all text that doesn’t have this character style

1. Save a copy of the indesign file. We’re going to make a mess of this file and you don’t want to accidentally save over the real InDesign document.
2. Delete every character style in the character styles list except the one you’re interested in. It’ll ask you what to replace each one with. Replace each one with [none].
3. Open the Edit > Find/Change window (ctrl-f). Switch to ‘GREP’
4. In the Find what: box, enter .* (this will match everything). Leave ‘Change to:’ blank.
5. In Find formats, under Character Style, choose [none].
6. Hit Change all. Everything should be instantly deleted except the text in that one remaining character style.

2: Copy all the remaining text from this indesign file

Export as HTML and copy from there.

1. File > Export
2. Choose the format to be HTML. Save this HTML file somewhere.
3. Open it up in a browser. It’ll be a hideous monstrosity to look at – this doesn’t matter.
4. Select all (normally ctrl-A). Copy.
5. Paste into a plain text editor: e.g. Notepad if you’re on Windows, or if you’re on a Mac, Textedit after using Format > Make Plain Text. This scrubs out all images and formatting, leaving just the text.
    6. Delete that hideous HTML page before anyone sees it…
6. Tidy up the text as needed – e.g. you’ll probably want to find & replace away unwanted paragraph breaks.

3: Profit