We do not have the original manuscript here; and the nearest fragment is almost three manuscript lines away, so we cannot tell from spacing considerations whether idle was in 𝓞. In the printer’s manuscript, Oliver initially wrote “the more part”; then somewhat later (with heavier ink flow) he inserted idle supralinearly. There would have been no reason for Oliver to have made this substantive change in the reading except that 𝓞 read “the more idle part”. Elsewhere in the text, there are 13 other examples of a modifier occurring between more and part:
The first example (“a more history part”) is quite striking, given the indefinite article a and the use of a noun rather than an adjective as the modifier between more and part. The phrase “the more part” is quite frequent in the text (occurring at least 23 times), so it is not difficult to understand why Oliver initially wrote “the more part” here in 𝓟. (For two additional cases where the original text may have read “the more part”, see under Helaman 6:21 and 4 Nephi 1:27. Parallel to 2 Nephi 4:14, there is also one example of “a more part”, in Helaman 6:32.)
Summary: Maintain in Alma 22:28 Oliver Cowdery’s corrected text in 𝓟, “the more idle part of the Lamanites”, which was undoubtedly the reading in 𝓞 (not extant here).