[& inserted in the margin, at the beginning of the line, with the same level of ink flow]
Here we have two examples where scribe 2 of 𝓞 momentarily skipped the and. Throughout this part of 1 Nephi, there are five other examples of this tendency on his part:
Except for the last case, scribe 2 caught his error; in the last instance, Oliver Cowdery supplied the and, which seems required. Of the corrections made by scribe 2 himself, only the first case (here in 1 Nephi 12:11) has a different level of ink flow. In the last of scribe 2’s own corrections (the one in 1 Nephi 13:20), there is an erasure, which indicates an immediate correction. The preceding five corrections were probably done when scribe 2 read back the text to Joseph Smith, since in each case the placement of the ampersand indicates that the basic text had already been written. The first one ended up with a weaker level of ink flow, but the ink flow for each of the next four is unchanged, which suggests that these corrections were not due to later editing on the part of scribe 2.
The biblical style (based on the Hebrew) uses and ’s between sentences to create a continuously connected narrative. In each of these cases, the abruptness without the and definitely seems inappropriate.
Summary: Scribe 2 of 𝓞 tended to accidentally drop the connective and when initially writing down Joseph Smith’s dictation; nonetheless, when checking the text, probably by reading it back to Joseph, he was in most instances able to restore the missing and.