A key utility of outlines is that you can see the structure of very large documents, yet zoom in on any one part. “Hoisting” allows you to do something in between. If you select a header in some outliners and hoist that header, what you get is a view of the outline as if only the structure under that one header existed. You could, for example, have a whole book in one outline, but work on outlines of chapters in isolation by hoisting.

OmniOutliner Before Hoist

OmniOutliner After Hoist