The left side of Kate has always had a list of open documents, which works well. At some point, a selector was added to choose between Documents, Projects, or other plugins. That was fine. But with 22.08, it's become rather large (40x40?) icons instead, which don't indicate what they are (unless you open the tooltip) and waste a lot of screen space. There appears to be no way to turn it off or make it smaller.
Check settings-Behavior and choose the style you want.