AND if you want to do it throughout a directory structure, you have to choose "Flat View" and Select All. Otherwise it only gives you a folder-by-folder option.
OK, having got that far, how can I show only the names that will be changed? I don't care about the filenames it's going to leave alone.
Or at least show the proposed changes at the top.
Or do I have to go through a long alphabetical list, looking for that faint bolding to show me what it proposes to change?
See the image. I don't care about the No change files.
You shouldn't need to use Flat View if you're using the options to rename and preview files in sub-folders.
I don't think there is a way to hide unaffected and/or turned-off files from the preview, other than to avoid selecting them before opening the dialog. (In the example in your screenshot, you could use Tools > Find Files to find all files with "Old" in them, then rename those. But that might not make sense with all renames, of course.)
Being able to sort, hide or group the preview list based on which items will change isn't a bad idea, though. (I'm surprised no one has asked for it before, in fact.)
But you're right that doing a search on the old name and then Select All/Rename will cull out the names that won't change. (And it has the added bonus of automatically formatting the list in Flat View.)
But that's kind of a workaround, sufficient for my purposes. It would be useful if you could just toggle the Rename preview to show only names to be changed, without a pre-sort. "Rename" is a scary function because it's so powerful, so the more control the better. (Speaking of which, an Undo function built into the Rename dialog would be useful.)