I am preparing a long list with entries and sub-entries
After I am done, I want to sort it by alphabetical order
But I want the sub-entries to stick with their parent entries, even after the sorting.
How to prepare the list, and how to sort it when I am done?

EDIT: to clarify, the project is to translate a book index into another language.
After I am done, it will have to be re-alphabetized, because the entries in the target language will not start with the same letter as in the source language.