They are best developed as the field work proceeds and before the corpus is too large.
an exercise: Given a research topic about race or gender in American politics, generate five to ten items to index from a the first four paragraphs of a report from the New York Times about Ben Carson (October 26, 2015)
There are still very few studies segmenting a population by gender category except in a euphemistic way (i.e. only two "genders" are considered)
An index entry is pre-theoretical in the sense that it is not designed to be used by anyone but this particular analyst. It is not intended to be used by anyone else, and, above all, it is not intended to be made public (and thus justified, defended, etc.).
Some students I know have used one of these programs with some success.