Active window control allows to save on vertical screen real estate by hiding the titlebar and moving its content into the control bar. While this works decently well this means the active window will always be displayed twice. once in the task manager and once with active window control. this will never look cohesive, is a little confusing and it wastes space. 

The only way to solve this would be to combine the 2 components. When maximizing a window its title bar content would be displayed in place of the application tab in the task manager. The space would be scaled to fit the title and the window decorations. optimally this would be rendered in the system set window decoration style and add tab visual cues that connect the title entry with the maximized window below.

There used to be a netbook mode for mate and there is active window control for kde but none of them was ever a cohesive experience. this would be a great way to set kde apart from other desktops on small screens by using space efficiently and elegantly. especially landscape devices like the steam deck and small laptops could profit from that.