Assuredly, the greatest moment for Nephi, the son of Nephi, occurred next in the Savior’s visit in Bountiful when he (the former high priest) was recognized and called out of the multitude by Jesus Christ (the eternal high priest; see Psalms 110:4). Nephi bowed down and kissed the feet of the Savior. That was a very tender moment. Jesus then called Nephi to even greater service and gave him, along with others, the authority and power to baptize the people. Jesus taught this and many of the primary core Christian principles that He had taught in Judea before his ascension (3 Nephi 15:1).
The visit of the Savior increased Nephi’s knowledge and authority as he was called to a leadership role in Christ’s church and was given further training. Nephi was present for the most glorious occasion of the Sermon at the Temple with its associated stages of ritual ascent. Although these experiences would be enormously great moments for everyone and anyone, Nephi must have been most deeply affected by them. He made special efforts to record these details. He also continued the rest of his life to serve the Savior along with his people, whom he loved, with all diligence, as did his son, yet another Nephi.
Records were kept leading up to the coming of the Savior. Meticulous records were then kept of the very words that Jesus spoke as He appeared to and taught the Nephite people. It seems to me that as the high priest, Nephi would have been the one who at least oversaw, if not actually conducted, the recording of these most sacred records.
Under the Law of Moses, only one person—the high priest—was allowed to go alone into the Holy of Holies in the temple. Thus, how amazing it must have been to him and to his people, that he could now share the glorious blessings of the Holy of Holies with all of them. Now, all of his people had the blessing to stand in the presence of the Lord—one by one—and see his countenance smiling upon them.
Book of Mormon Central, “Why Should 3 Nephi Be Read as the Book of the High Priest Nephi? (3 Nephi title and heading),” KnoWhy 577 (September 8, 2020).