I have connected a Set Role operator to a ReadARFF operator to change an attribute role. When first clicking on the drop-down menu for paraemter 'name' all attributes contained in the arff file are displayed. Select a different operator. Select the 'Set Role' operator again. Clicking on the drop down menu 'name' displays only the already selected attribute name. Close the menu without deselecting operator. open menu again. All attribute names are displayed.