Unlike Trados 2007, Studio 2011 doesn't require a specific TM setting to store multiple translations for the same segment in the TM. All we need to know is the right keyboard shortcut when committing a new translation to the TM.
To store multiple translations for the same segment, simply use Ctrl+Alt+Up (Add as new translation) to commit the new translation to the TM. Note that this keyboard shortcut is user-changeable via Tools-Options-Keyboard Shortcuts-Editor > TM Window.
When a segment comes up for which there is more than one translation in the TM, simply use Alt+1, Alt+2, etc. to choose the relevant translation to populate the target segment.