I prefer Style 2

Style 2
Its easy to find what u need without going through too many clicks and the page directory on the right makes it simple to jump to any section quickly. It just feels straightforward and not overly complicated.

I like Style 2 the best.

Three levels gets you to a natural stopping point (Release Notes → Overview → Major Features), while finer items like "New Features" or "Check Service Status" become in-page anchors in the right-hand directory instead of extra clicks. It matches how content is already chunked, so it's a nav change, not a rewrite of the hierarchy.

One catch before committing: check whether your deepest trees (upgrade guides, troubleshooting cases) are actual headings that map to a Page Directory, or separate articles. If they're separate articles, no nav style fixes the click count — that's a content/Information Architecture issue to flag separately.

I prefer design style 2

I like style 1

I prefer Style 3

Style 3 is better than other, more simple and useful

I prefer Style 2.

It provides a good balance between simplicity and detailed navigation. Having three levels in the left sidebar makes it easier to understand the document structure, while the Page Directory on the right helps users quickly jump to specific sections within long technical documents. This would be especially useful for troubleshooting and configuration guides.

I prefer Style 3
look simple and usefull

I prefer to style 2, with search feature.