SE Steam Edition has built-in Chinese, but I think that is not perfect
1.If I type a Chinese sky object such as "地球" (Earth), the finder under the searchbox won't show "地球", I need press Enter or "确定" (OK) button then it selects "地球/Earth".
2.If I make an addon that use Chinese object name, then it will become some Greek and English letters in the finder under the searchbox and even I press Enter, it still tells me cannot find that object.
1: the object finder shows names from integrated catalogs, which are loaded by the program in early stages and compiled in English . Translated names are saved in databases, one for each language, and are dinamically loaded by the program, you can change language on the fly. It can't list that database in the object search window, probably because of program limitations. It's a problem not only specific to Chinese, but for all existing localizations. You can use those names as you said by pressing ok or goto.
2: Greek letters, used by the Bayer designation, are transliterated in SE catalogs with first three letters of the latin alfabet, so it can happen that some object named "alfabet" could appear as [ALF]a[BET]. it's a problem that will be solved eventually. This could also lead to a "object not found" error.