@Gregory Jones Yeah, it's definitely the Custom Lists permission under the Setup subtab in permissions as @karlenigma said. I don't think there's a way to separate the plus sign adding option from the customization menu editing, if that's what you're after. Regarding your workflow question - I believe this is possible. You need to set your Trigger On option for your action to a client-side trigger (like After Field Edit). Then you'll be able to select the Trigger Client Field to say which field being edited should prompt the error.