A repeating group will only show the entries that are stored in the database and that appear in the data source search. To do what you need to do, you need to store each line as they are made. You should add an input group below your RG so that looks the same as your RG, this will have input elements. when you click save, it adds the Article to the database.
If you want to keep these separate from other entries until the import all button is clicked, then you should setup either a shopping basket system, or use states or categories for Articles not imported.