I wasn’t aware that PDF Index Generator could also create a back-of-the-book index by…

importing a list of terms from a text file, to index a book using just that list of terms.

Useful. There’s a new video tutorial showing how to do this.

This means that one could manually go through a digital book in an armchair, just jotting down specialist terms or phrases while also proofing. No need to note page numbers. The resulting mini-index could then be merged with the larger automated one.