Answer
No — there's no system-level setting to suppress this confirmation message across the board. It's controlled per PL/SQL-Block-type custom menu, per user, and the user's choice is stored in their own personal profile, under the path 'User/Windows/Application/ContextMenu,' as a True/False value for that specific custom menu action. Since it's stored in the user's profile rather than a global setting, there's no single switch to flip that would apply the suppression for every user and every custom menu action at once.