Elsewhere in the Book of Mormon text, the verb unfold is always followed by unto when the object of the preposition is a pronoun:
When the object of the preposition is not a pronoun, we have two occurrences with the preposition to but none with unto:
In the history of the text, there are numerous examples where scribes have mixed up the prepositions unto and to. We have examples of changes occurring in both directions; for a couple of examples, see 1 Nephi 15:33 and 2 Nephi 6:6. Such variation implies that we should consider each case on its own merits. With respect to 1 Nephi 10:19, both to and unto can occur with the verb unfold, so there is no reason to reject the to found in the earliest textual source for that passage.
Summary: Restore the preposition to in 1 Nephi 10:19 (the reading of the original manuscript) since either to or unto can complement the verb unfold.