Just creating this issue as a consolidation of anything to do with localization as well as a quick overview of what would need to be done if you wanted to contribute in translating.

Below are the two files that would be used as a reference when creating a new localization and empty slates for languages can be found in the parent folder of these files.

English Localization File

Update: Since apparently there is a localization page directly on Curse it might be better to use that system. I have also merged the files into one because that is how the Curse system handles it and will make the exporting of any translations there easier.

It is very likely that I have missed things that would need translations, please do point them out if you notice any.

Great！
The Chinese localization files will be updated by my friend in a few hours.

Thank you, I figured I missed some. I'll add them as soon as possible.

I will have to look into why it says both things about the "Default" profile because it really shouldn't have.

As for the "Default Profile" name, with the current way the "Default" profile is handled it is important that the "Default" part stays. I will look into it and see what I can do about localizing that as well, but for now it will need to stay as is. The "Profile" part however could be translated without issues if that doesn't make it weird in Chinese to have the two mixed for now.

Anyway, some my friends like use Chinese word "万"(1万=10 thousands) and "亿"(1亿=100 million) to describe HP approximatly . Do you have any plan to add an option about it?

I didn't have any plans to do so, mostly because I had no idea you shortened it like that. I'll see what I can do as this would only be a thing for the Chinese region I'm guessing.

Is "K"(thousand) and "M"(million) used as well and would you like those to be added to the locale in that case?

Yes, both are used. I used to add an option Use Chinese Number in Funky Stuff in earlier translations for my friends.
I have also made some modification in this version, maybe it will be useful.
NeatPlatesHub\functions\Text.lua
NeatPlatesHub\Hub.lua
NeatPlates\locales\enUS.lua

I was considering just doing it like this

if LOCALE_zhCN and number > 100000000 then
	return (ceil((number/10000000))/10).."亿"
elseif number > 1000000 then
	return (ceil((number/100000))/10).." "..L["M"]
elseif LOCALE_zhCN and number > 10000 then
	return (ceil((number/1000))/10).."万"
elseif number > 1000 then
	return (ceil((number/100))/10).." "..L["K"]
else
	return number
end

So that this would just automatically enable if it detects that localization. Unless there is some reason for it not to automatically be enabled? Also do you happen to know if this is also a thing for the "zhTW" localization?

I have made Chinese translation, but I found some parts aren't listed in profile page:

1. "Categories"(目录) button at upper right corner;
2. Given ranges like "9 yards"(9 码) in "Other Widgets";
3. The name of "Default Profile"(默认模板).
   Do them need to be translated?
   Chinese localization file:
   zhCN.txt

Another issue: The messages "Sorry, can't delete the Default profile :(" and "The profile '%1' was successfully deleted." are both shown when I try to delete Default Profile.

They are "萬" and "億" for zhTW localization, and "w" and "e" for enUS one.
It will be well to automatically enabled for zhCN and zhTW, but I suggest this number be an preference option for WoWers, which performs like Skada.