Hello @jwzegelaar,
Thank you for reaching out to us. The resource system of Cinema 4D does not support Unicode encodings directly. Strings that contain characters outside of the ASCII table must encode Unicode characters. Here is for example the start of the Japanese string definitions for the Asset Browser as they can be found in {C4D}\resource\modules\assetbrowser\strings_ja-JP.str
:
STRINGTABLE
{
IDS_ASSET "\u30A2\u30BB\u30C3\u30C8";
IDS_ASSET_MANAGER "\u30A2\u30BB\u30C3\u30C8\u30D6\u30E9\u30A6\u30B6";
IDS_ASSET_MANAGER_CMD "\u30A2\u30BB\u30C3\u30C8\u30D6\u30E9\u30A6\u30B6...";
// ...
}
This applies to both dialog and description resources. Most text editors such as VS Code
offer plugins or native features to Unicode escape file contents. We recommend using such tools to produce the escaped strings for translations.

Cheers,
Ferdinand