i need to nest a Registration list view inside a TrainingEvent data view, to only show those registrations that belong to this training event. i added a new full width row to the page. Dragged a new data view into the new row, and wanted to connect this data view to the TrainingEvent entity. However, when i select entity TrainingEvent, the select button is in grey. also, the Add button has a number 1 on the top? thanks for answering:-)