The Druid contains CJK language example - druid 1.0. You can select languages and see how it looks.
Druid Example using already prepared CJK font with set of all localization characters (I use editor_script from defold-lang to collect them: https://github.com/Insality/defold-lang/blob/main/USE_CASES.md#use-editor-script-to-collect-unique-characters)
To prepare your font (to merge CJK with your current one) you can use FontForge to do that. It has option to “merge” fonts
If you have several fonts, it’s possible to use only one of them in your GUI files. The font resource can be changed with something like `go.set("#gui", “font”, {key = …}). So the live-update with downloadable fonts should be available too
Also there is new extension https://github.com/defold/extension-fontgen. It can generate a font texture to use and seems can be useful also to prepare your fonts with set of characters runtime if usefl