Looking for examples of how to use this feature.“Use preview list to build macros”
There's a video example here:
Which is from the Opus 12 release notes section on new Rename features, that describes things in text form if that helps understand what's going on: https://www.gpsoft.com.au/help/opus12/index.html#!Documents/Opus12/Rename1.htm
But you basically just turn on the checkbox you mentioned and then start editing the names underneath it. Any changes you make will be applied to all names at once.