Menu Item Separators and Line Breaks
Windows provides a special type of menu item, called a separator, that appears as a horizontal line. You can use a separator to divide a menu into groups of related items. A separator cannot be used in a menu bar, and the user cannot select a separator.
When a menu bar contains more menu names than will fit on one line, Windows wraps the menu bar by automatically breaking it into two or more lines. You can cause a line break to occur at a specific item on a menu bar by assigning the MFT_MENUBREAK type flag to the item. Windows places that item and all subsequent items on a new line.
When a menu contains more items than will fit in one column, Windows automatically breaks the menu into two or more columns. You can cause a column break to occur at a specific item in a menu by assigning the MFT_MENUBREAK type flag to the item. Windows places that item and all subsequent items in a new column. The MFT_MENUBARBREAK type flag has the same effect, except that a vertical line appears between the new column and the old.
If you use the AppendMenu, InsertMenu, or ModifyMenu functions to assign line breaks, you should assign the type flags MF_MENUBREAK or MF_MENUBARBREAK.