One wonders if the plural chief judges here is a mistake for the singular chief judge. There is evidence, to be sure, that Oliver Cowdery occasionally miswrote chief judge as chief judges:
Here in the original manuscript for Alma 46:34, Oliver Cowdery initially miswrote the noun as Judgees, a slip of the pen that ended up repeating the e vowel. Oliver erased the final es, then overwrote the erased e (the second one) with an s. But the fact that he wrote the s a second time argues that the plural reading was intended.
Since Moroni would have been in charge of all the armies of the Nephites, it seems as if the appointment might have been reserved for “the chief judge over all the land”. There are 36 instances in the text of chief judge that refer to this supreme chief judge. Of course, each land also had its own chief judge (“the chief judge of the land”); there are eight instances of chief judge that refer to the chief judge over an individual land: six to the chief judge over the land of Ammonihah (in Alma 14:4–27) and two to the chief judge over the land of Gideon (in Alma 30:21, 29). Nonetheless, there are three other references to chief judges in the text (although these are found only later in the text):
None of these passages refer to these chief judges as acting as a single body to make a decision (as in the current text for Alma 46:34). Still, these examples show that the plural usage is possible. In fact, in Alma 46:34, the reference to “the voice of the people” suggests that there was a national vote of approval for Moroni, which could imply that all the chief judges were involved, not only the chief judge over the entire Nephite nation but also the chief judges over the individual lands.
Summary: Accept the plural chief judges in Alma 46:34, the reading in 𝓞; the plural is acceptable since the whole Nephite nation was involved in the selection of Moroni as chief commander.