The Palette Menu for 10.3 is now available for download.
As for multi-column, I’m not sure what you are referring to. You can use the Palette Menu to group pages into separate categories which show up as cascading menus, but it is not really column based.
The multi-column “thing”, as far as I can recall, was a solution to what happens when the groups are so numerous that exceed the vertical screen height. I do not know if there is a scroll capability or group-in-group to expand the menu horizontally.