Dual Columns submenus display check marks for Left Column, Right Column, and Normal (Full Width). If there are different column types in the selection, the “-” character is displayed to the left of the menu item, instead of the check (as is standard on the Mac).
If the user has displayed the column icons in the toolbar, then these show the STATE of whatever is selected. As with the character formats (bold, italics, underline) if there are multiple column types in the selection then multiple icons are shown as toggled.
The textual (L) and (R) have a graphic icon next to the style popup. A (-) is displayed if multiple column types are in the selection (see images, below):
