Had tried looking over several times but still can't find Traditional Chinese or zh-tw in "Add Locale" list.
It's hard to believe because this list contains a huge amount of locales, including even the locale that might not be used by anyone like "Zhuang; Chuang".
Is there a way using Android Studio to add translations of Traditional Chinese?
Open "src\main\res" directory of your project in the explorer/finder, you will see the folder "value-zh" if you added Chinese in Android studio.
Simply make a copy and rename them to: "values-zh-rCN" for simplified Chinese and "values-zh-rTW" for all traditional Chinese
And android studio will automatically recognise that:
See this as an example: https://android.googlesource.com/platform/packages/apps/Settings/+/master/res/
See more from this answer: Simplified and Traditional Chinese vs Regions
