Oliver Cowdery initially omitted the yea here in 2 Nephi 4:35, but he restored it somewhat later, perhaps while proofing 𝓟 against 𝓞. (The yea was supralinearly inserted with a sharper quill; thus the correction is not immediate.) Nonetheless, there is no strong need for the yea here, which means that there was no motivation for Oliver to have added the yea on his own. Of course, the use of yea is common throughout Nephi’s psalm; counting this occurrence, yea occurs nine times in just 21 mostly short verses (from verse 15 through verse 35).
Summary: Maintain each yea throughout the psalm of Nephi (2 Nephi 4:15–35), including the one in verse 35 that was inserted later in 𝓟.