To add/remove edit and list boxes controls for the window, you need to select "Edit Boxes and Listboxes" tab.

     You can see, that the content of this tab panel is very simple. You could here:
1. Create new control. Use "Add New Edit Box", to create new edit box, and "Add New Listbox" - for new listbox.
2. Delete selected control. Use "Delete Selected Edit Box", to delete edit box, and "Delete Selected Listbox" for listbox.
3. Change the order of control creation. There are "Move Selected Edit Box Up" and "Move Selected Edit Box Down" for edit boxes, and "Move Selected Listbox Up" and "Move Selected Listbox Down" for listboxes.