Scribe 3 of 𝓞 first started this sentence without the sentence-initial and, but somewhat later he inserted it inline (as an ampersand) and with somewhat heavier ink flow. Without the and, the sentence-initial behold sounds quite abrupt. It is possible that the inserted and is not original, but unlike the case with scribe 2 of 𝓞, there is no independent evidence that scribe 3 frequently omitted and ’s. Without additional evidence, it is more reasonable to assume that the and is original to the text and that it was discovered missing when scribe 3 read these words back to Joseph Smith (as part of the dictation process), which would explain why the correction was done with somewhat heavier ink flow.
Summary: Maintain the sentence-initial and before “behold I saw the multitudes which had not fallen”.