I seem to have inadvertently turned off the warning when i try to add to a relation an object that's already a member. Where can I find the option to re-enable it? I searched the advanced preferences for relation and duplicate with no joy.

I seem to have inadvertently turned off the warning when i try to add to a relation an object that's already a member. Where can I find the option to re-enable it? I searched the advanced preferences for relation and duplicate with no joy.