The original manuscript is extant for about half of this passage, and it shows that Oliver Cowdery initially wrote shewed rather than the correct shewn in 𝓞. Oliver erased the ending -ed and overwrote it with an n; the erasure shows that the correction in 𝓞 was immediate. The past-participial form shewn has been maintained here except for the expected change to the modern shown in LDS editions, beginning with the 1888 large-print edition.
For the verb shew /show, there has been some minor competition between the past participle ending in -ed and the one ending in -n, with the latter dominating. For some discussion, see under Helaman 15:3; also see under 1 Nephi 11:9 for some additional statistics. For a complete discussion and listing of every form of the verb shew /show, see under shew in volume 3. In choosing the past-participial ending (either -ed or -n) and the spelling for the vowel in this verb (either ew or ow), we follow in each case the evidence from the earliest textual sources. Thus here in Ether 5:4, the original manuscript (and apparently the original text) read shewn.
Summary: Restore in Ether 5:4 the past-participial verb form shewn, the immediately corrected reading in 𝓞.