Hi
May I ask where did you take this phrase from?
I suppose it's a philosophic saying (probably from Aristoteles). In order to translate it properly you must know the context.
The meaning of "τέχνη" in a philosophic context is usually "skill".
You know the context and I think you are right that the most appropriate translation of trade/craft for this phrase is "τέχνη". So one possible translation in Greek would be: “Η τέχνη μου είναι η αρετή”.
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.