The palette shows a status of elements selected in the model (zones and objects) in terms of their relation with rooms and items planned in dRofus. It also provides an interface for changing that status (linking and unlinking zones and objects) and a navigation tool (Open RDS).
It does not appear automatically when you run ArchiCAD. You should explicitly open it through the dRofus menu each time you open a model. You will be prompted to login to a project before you see the palette.