Hi.
You can add your new position here. Then it will appear in the list of positions. This will be erased when template updating, but the position will continue to work if at least one module was published in it. After removal when updated, this will disappear from the list of positions but will remain in the list of active positions in a module settings and in the template settings.
Therefore better use a simpler way. Just type any position name which you came up with when publishing a module and then it will appear in the Active positions list in a module settings and in the template settings.