You probably still mix up things as a newbie

Tables are data structures in memory and "hiding columns" sounds more like listviews in GUI. They aren't related, but you can convert data in tables into listview entries, and vice versa. Learning how data resides in tables is important for any more complex projects, so I suggested to read about them from the documentation. It's then quite trivial to use the data in tables for any other things.
1. Do you mean hiding a column in RapaGUI's listview?
2. Hmm.. something about swtich-case statement or what case?