Is it possible to block non-Latin characters such as Kanji, Cyrillic, or Greek letters with Address Ninja?

Yes. On the Pro plan, open Custom rule (REGEX), click Presets, and choose Allow only Latin characters. This preset blocks every character outside the basic Latin set, including Kanji, Cyrillic, and Greek letters. It also blocks accented letters such as ü or é. To block Cyrillic letters only, choose Block Cyrillic letters. Select the fields and countries, then click Save and turn on.