I offer to include articles in the left-side tree. Currently it only shows categories. When user clicks a category, a default first article from this category is displayed. This way, user can't see other articles in the category, only Next and Previous buttons.

Also, it is possible to click on Category name at the top breadcrumb- in this case all articles from a category will be displayed. However, almost noone can find this possibility.

This all leads users to get lost in the knowledge base - they don't see all articles and can't navigate as the wish - by selecting desired article, instead of clicking small Next and Previous buttons.

I'm fully sure that knowledge base user should be able to move into ANY desired article, and list of articles should ALWAYS be visible in selected category.

Attaching screenshot of documentation center which could serve as good example of what I offer.