Drag and Drop's right-hand pane shows the accessible data sets on the mainframe. When there is a large number of data sets on the mainframe it can be difficult for you to focus on only the data sets you are interested in, so Drag and Drop enables you to hide items from the right-hand pane.
By default, the right-hand pane shows all accessible mainframe items, and in this mode it is referred to as the Active Mainframe Item View. If you do not want to see an item in the Active Mainframe Item View you can hide it by moving it to the Hidden Mainframe Item View. Hiding items does not change them in any way; hidden items are removed from the Active Mainframe Item View and added to the Hidden Mainframe Item View, and you can switch between these two views as and when required. You can restore items from the Hidden Mainframe Item View back to the Active Mainframe Item View, and you can even view hidden items in the Active Mainframe Item View.