Did submarines lay magnetic mines in World War II?

Were magnetic mines ever laid by submarines during World War II?

Possibly, but aircraft were the primary and easier delivery method, and submarine use would need operation-by-operation confirmation.

Confirming submarine use would require checking individual minelaying operations, so the answer remains qualified. Magnetic mines were practical to deliver by aircraft, which made aviation the primary deployment method. That advantage reduced the incentive to adapt scarce submarine capacity for the same task. Technical possibility alone does not establish that a method was used at operational scale.