Pages v5.5.3 has no true outline capability. You can attempt to make an outline using the list functionality, but it will drive you mad. Here is an example (click image to enlarge) of the Outline facility in Mellel 3.4.3, which has a free trial, and is also in the OS X App Store. MS Word has had true outlining capability for eons.

The outline templates in Pages '09 v4.3 that were omitted in all releases of Pages v5. There are no explicit Outline tools in Pages '09, and there is an optional Toolbar item called Outline, that toggles between headings and text, and an improvised Outline view. If you still have Pages '09, this may be a minimum match for your outlining needs.
