You want to separate menu items into groups using horizontal lines.
Create a new menu item that will act as a separator by setting its style to SWT.SEPARATOR .
Here's an example that creates a menu separator and adds it to the File menu:
fileMenuSeparator = new MenuItem(fileMenu, SWT.SEPARATOR);
9.13.4 See Also
Recipe 9.7 on creating a menu system; Recipe 9.8 on creating text menu items; Recipe 9.9 on creating image menu items; Recipe 9.10 on creating radio menu items; Recipe 9.11 on creating menu item accelerators and mnemonics ; Chapter 8 in Eclipse (O'Reilly).