After looking at both sides of this debate, I now believe 1 John 5:7 is God’s Word.
One reason is because old Waldensian Bibles (long before Erasmus) contained the full 1 John 5:7.
I devote an entire chapter in my book to this controversy. The text says: “There are three … the Father, the Word [Jesus], and the Holy Spirit; and these three are one [united].”
EGW herself confirmed this basic truth when she wrote: “There are three living persons of the heavenly trio; in the name of these three great powers—the Father, the Son, and the Holy Spirit—those who receive Christ by living faith are baptized … ” Special Testimonies, Series B, Vol. 7, p. 39." Steve Wohlberg/F7