Here scribe 2 wrote thse in 𝓟. John Gilbert, the 1830 compositor, set these; since Gilbert’s copytext was 𝓞 for this part of the text, 𝓞 probably read these. One other possibility is that scribe 2’s thse was an error for those, which would mean that not only did scribe 2 omit the o but that Gilbert replaced those with these. Such a scenario is highly unlikely, but one wonders about the possibility that the original text here read “save it were those few plates which I gave unto my son Moroni”, as if the plates that Mormon is writing on here are distinct from the ones he gave his son. Ultimately, since Moroni takes over for his father Mormon at the beginning of chapter 8 in this book (at the beginning of chapter IV in the original chapter system), it seems more likely that the plates are the same and therefore these is appropriate.
Summary: Maintain in Mormon 6:6 the demonstrative these, the 1830 reading and presumably the intended interpretation for thse in 𝓟.