Style Modifications in OmniOutliner 4

May not be immediately obvious. The first (Style) tab of the Inspector window modifies the selected style, but make sure no text is selected, otherwise the change is applied to the text selection rather than the selected style. Typically this means clicking in an empty document area first to get a clear selection.

http://forums.omnigroup.com/showthread.php?t=28928&page=4