The printer’s manuscript has hide (that is, without the -eth ending), while the 1830 edition has the third person singular form hideth. Perhaps hide could be thought of as the first person singular form, in agreement with the first person I rather than with the third person the same.
Elsewhere in the text, we consistently have the third person singular ending -eth for this construction (“I am X ”), where X is a subject complement:
The last example has the same, just as here in Mormon 8:14. Thus internal evidence supports the 1830 reading in Mormon 8:14.
Changes in the early transmission of the text show that the -(e)th ending can be either added or omitted. There are no examples involving scribe 2 of 𝓟, but there are five cases for which Oliver Cowdery was the scribe (two involve omission of the ending, each marked below with an asterisk):
There are also four examples where the 1830 typesetter made the change (of which only one involves the addition of the ending, marked below with an asterisk):
These examples show that the errors can occur in either direction. The following scenario is also possible here in Mormon 8:14: Oliver Cowdery omitted the ending -eth when he took down Joseph Smith’s dictation (here Oliver is the presumed scribe in 𝓞), scribe 2 of 𝓟 copied hide since 𝓞 read that way, and the 1830 typesetter supplied the expected -eth. Since the transmission evidence is mixed, probably the best solution here in Mormon 8:14 is to accept the internal evidence, thus maintaining the 1830 reading.
Summary: Retain the 1830 reading in Mormon 8:14, hideth, since we expect the third person singular ending in this construction (“and I am the same which hideth up this record unto the Lord”).