The Script File is the path to the Python script that will be executed when you click the launcher. When you click the Add button, all the settings for the new launcher are saved to an XML file in the directory specified in the Folder box. On start-up QtiPlot parses all XML files in this folder and creates the corresponding menu items or toolbar buttons. When you press the Remove button, the launcher selected in the left side list of the dialog is removed from QtiPlot menus/tool bars and the corresponding XML file is deleted from the hard disk. Make sure that you have backed up the file if you will ever need it in the future!