Readers comparing the Spanish edition of The Great Controversy to the English original may be surprised to learn that the Spanish version contains an additional chapter—chapter 13. The origin of this chapter is explained in The Later Elmshaven Years, [vol. 6 of the Ellen G. White Biography series,] p. 377, as follows: 

As the work of the church was broadening to take in many countries and many languages, steps were taken to translate the new book so that the peoples of many tongues might read. One of the first was the Spanish, undertaken almost immediately. As this work was entered upon, it was observed that no place had been given to the reformation in Spain. As counsel was taken with Ellen White, it was decided it would be well if in the Spanish printing, a supplementary chapter compiled by competent writers could be added. Thus, the Spanish Great Controversy carries forty-three chapters in place of the forty-two in other printings. Chapter thirteen in that book, titled The Awakening in Spain, is clearly designated as a work of “collaboration” and has a footnote stating: GCMC 1.1

This chapter was compiled by C. C. Crisler and H. H. Hall, and was inserted in this book with the approval of the author.—Page 252. GCMC 1.2

Consequently, there has never been any missing chapter from The Great Controversy. This non-Ellen White material has always been available in the Spanish edition, and it was never intended by her to be a part of the original English edition. GCMC 1.3