Nephi understands that he has inserted an aside, and notes that he will later give an account of the making of these plates. That future account in 2 Nephi 5:29–31 will be much more abbreviated than the two accounts from 1 Nephi 9 and 19. Nevertheless, the 2 Nephi account occurs in the correct historical timeframe, where the two in 1 Nephi are out of temporal sequence.
An important transition occurs in these verses. Nephi mentions making the plates, and then speaks of what he is writing on them. He says: “this I do that the more sacred things may be kept for the knowledge of my people. Nevertheless, I do not write anything upon plates save it be that I think it be sacred.” This mention of sacred things is the trigger for the next section of his text. As with other triggered asides, this was not part of the original plan.
Nephi clearly had a plan and an outline. However, when he began writing on the plates, it appears that he was able to compose new text on the fly. There is no evidence that he was copying a text, so his mind was engaged in the process, and these asides show Nephi when he is inspired by something he wrote, so that he provided additional material.
In this case, the mention of sacred things leads directly to a discussion of Jehovah’s earthly mission, developed in the next set of verses.