I like to see movies titles in their original language because I speak some languages, however I cannot reach Arabic, Cyrillic, Japanese, Chinese, and non latin alphabets in general. For this reason, I’d like to have a checkbox in the library settings to use original titles using only latin characters.
Do you mean when in those languages to not use the Original Title?
The metadata sources from where Plex is drawing unfortunately don’t have a field which contains the “original title, transliterated to latin”.
They only provide the original title (in the source alphabet), the localized version of the title in a certain language, and some alternative titles (which Plex can utilize for better matching).
If I understand correctly, then TMDB does not provide the latin transliteration. Because I see that IMDB does it.

Just throwing in that there’s already an existing suggestion discussing an option to set the preferred alphabet for items or the entire library (especially in combination with original titles).
I suggest you comment/vote in that thread in order to help us avoid distracting or cannibalizing votes — closing this thread as a duplicate.
2024 clean-up: duplicate