The 1840 edition added the adverbial up after did lift but not to lifting later on in the passage, thus creating variation in the usage here (“did lift up their eyes” versus “lifting their voices”). This addition of up is probably unintended and not due to editing. The 1908 RLDS edition restored the original reading lacking the up.
There are only two other occurrences in the text of “lift (up) eyes”, and these examples, both quotes from Isaiah in the King James Bible, have the adverbial up:
And this result for biblical quotations is not surprising when we note that the King James Bible has instances of only “lift up eyes” (59 times); there are no examples at all of “lift eyes” in the King James text.
But this result does not mean that the Book of Mormon text cannot have any instances of “lift eyes”. We can see this when we consider the corresponding phrase “lift (up) voice(s)”. The King James Bible has instances of only “lift up voice(s)” (36 times); there are no examples of “lift voice(s)”. In King James quotes in the Book of Mormon, not surprisingly, we get only “lift up voice(s)” (five times), but in the nonbiblical parts of the text we get variation, three cases with the up and two without (including the one here in Helaman 5:36):
(The 1874 RLDS edition omitted the up in 2 Nephi 4:35; for discussion, see under that passage.) The two nonbiblical instances of “lift voice(s)” therefore support the one case of “lift eyes”. In addition, there is a similar instance of the verb lift (in 3 Nephi 4:8) with their cries instead of their voices; here the up is also lacking: “the armies of the Nephites … did lift their cries to the Lord”. On the other hand, as before, the King James Bible has only the up, with two instances of “lift up (a) cry” (in Jeremiah 7:16 and Jeremiah 11:14).
Taken all together, the nonbiblical Book of Mormon examples indicate that in each case we should follow the earliest textual sources in determining whether the adverbial up occurs in phrases involving lift. The critical text will therefore retain the two cases of lift without the up here in Helaman 5:36.
Summary: In accord with the earliest text, maintain in Helaman 5:36 the two instances of the verb lift without the adverbial up: “and he beheld that they did lift their eyes to heaven … as if talking or lifting their voices to some being”.