In the original manuscript, compound ends in an s that shows no sign of erasure. Nonetheless, this appears to be an error on Oliver Cowdery’s part. We have other evidence of Oliver accidentally adding an s to a word, as in the following clear examples:
passage manuscript reading source
1 Nephi 22:17 unto the destructions of their enemies 𝓞*
Alma 21:5 there arose an Amalekites 𝓟
Alma 22:29 round about on the wilderness sides 𝓟
Alma 30:47 thy souls should be lost 𝓞*
Alma 41:2 the plan ... is requisites with … 𝓞*
Alma 47:1 to go to battles 𝓞*
Alma 50:32 he would obtain possessions of ... 𝓟*
Alma 51:4 there arose a warm disputes 𝓞
Alma 51:21 and the prides of those people 𝓞*
I have not been able to find evidence on the online Oxford English Dictionary or on Literature Online for such usage as “a compounds of X and Y”. The phrase “a compounds of X and Y” occasionally occurs on , but these instances all appear to be typos, simple slips as here in Alma 43:13. When Oliver copied the text from 𝓞 into 𝓟, he substituted the expected compound; the critical text will follow this emendation.
Summary: Maintain in Alma 43:13 the expression “a compound of X and Y”; the plural compounds, the reading in 𝓞, is probably a simple scribal error; occasionally in the manuscripts, Oliver Cowdery accidentally added a word-final s to nouns and adjectives.