Scribe 3 of 𝓞 wrote “thou hast shew” in the original manuscript. When Oliver Cowdery copied the text from 𝓞 into 𝓟, he corrected the shew to shewn. We have evidence that scribe 3 of 𝓞 occasionally omitted the final n of a past participle:
Another possibility is that the shew in 𝓞 actually stood for shewed. And there is also evidence that scribe 3 of 𝓞 occasionally dropped the regular inflectional ending -(e)d for the past participle:
Thus scribal evidence equally supports both shewn and shewed as emendations in 1 Nephi 11:9.
Elsewhere in the text, there are 37 examples of the past participle for the verb shew (and its variant show). Based on the earliest textual sources, we have the following variants: shewn (29 times), shewed (6 times), and shown (2 times). Thus the -n ending is favored most of the time (31 versus 6 times). Within the small plates themselves, there are 11 occurrences of the -n ending but only one of shewed (in 1 Nephi 20:6). Yet this one exception is a citation from the King James Bible, and there (in Isaiah 48:6) the form is shewed. In other words, the actual Book of Mormon language in the small plates consistently supports the use of shewn (or shown) rather than shewed. Internal evidence thus supports Oliver Cowdery’s decision to interpret the shew as a scribal error for shewn. (For the later LDS editing of shew to show, see shew in volume 3.)
Summary: Maintain in 1 Nephi 11:9 Oliver Cowdery’s interpretation of shew in 𝓞 as a scribal error for shewn rather than shewed.