Regardless of where your Add-on lives, it's important to create context around its functionality. Add-ons located inside of existing views, such as the table view, are naturally more likely to communicate their presence by default. For other situations, such as when placing an Add-on inside a right sidebar column or on its own tab, always use the title bar. This helps not only remind the user what functionality they're seeing, but in the case of an Add-on inside a new tab, it becomes a useful way-finding device.