Below the divider are named styles that you can apply wherever you like. Named styles can only be created with OmniOutliner Pro, but can be viewed with either Standard or Pro.
Drag the style chit from the styles palette and drop it onto the text, or just press the function key (F1, F2,...) associated with the named style you want. (Hold Command while dragging to apply the attributes of the named style without applying the named style itself.)