I readily admit I may be missing something, but to date I have found no solution to this matter. When creating structured documents in OmniOutliner, from time-to-time I will inadvertently create another row level. That, in and of itself, is very easy to fix by promoting—or in OmniOutliner nomenclature, “outdenting”—the row. Where the problem lies is that the row style remains despite the fact that no rows in the document exist at that level.
For instance, if I have a document that goes down to Level 4, accidentally indent a row to Level 5, and then correct its level back to Level 4, the Level 5 Rows style remains. If I right-click on the Level 5 Rows style, Delete Style is grayed. Is there a way to delete auto-generated styles when they are not in use?