In this passage there are two cases where the verb phrase “to be made manifest” is followed by a prepositional phrase headed by unto. In the 1892 RLDS edition, the preposition unto in the first case was replaced by to, but the original unto was restored to the RLDS text in the 1908 edition. In the second case, the whole prepositional phrase “unto me” was momentarily omitted as Oliver Cowdery took down Joseph Smith’s dictation. Oliver’s supralinear insertion of the phrase is in somewhat heavier ink flow; he probably made the correction after reading back to Joseph what he had initially written and discovering that “unto me” had been omitted.
The text is consistent in selecting the preposition unto for the verb phrase “to make manifest” (17 times); similarly, for the verb phrase “to manifest”, only the preposition unto occurs (32 times). Thus the 1892 replacement of unto with to in Jacob 7:12 is clearly an error.
Summary: Maintain the two prepositional phrases headed by unto in Jacob 7:12; the preposition unto is expected with the verb phrases “to manifest” and “to make manifest”.