Short answer: No. Mahavira did not speak about an "11th wonder" in Jain scriptures. That phrase is not part of the canonical teachings.

What might be meant:

• In Śvetāmbara tradition, the 11th Anga (the 11th main text) is Vipāka Sūtra, which is a Jain scripture dealing with the consequences of karma (the ripening of karma), not a “wonder.” It is simply the labeling of one of the Anga texts, not a topic Mahavira spoke about as a “wonder.” ( jainknowledge.com)

If you’d like to read more about the Anga system and Vipāka Sūtra specifically, you can check a JainKnowledge page that discusses the 11 Angā texts.