What miracles did Saint Columba do?

He was declared a saint long before the formal canonization process was instituted in the 12th century. She is 'precongregational.' In other Words, he was a saint before the Sacred Congregation for the Causes of Saints was created to investigate candidates for sainthood. No miracles were required at that time and the person was declared a saint strictly based on their merits and popular acclamation supported by a bishop. Today only the pope can declare a saint and only after an exhaustive study by the Congregation.