Features / Buttons explained

Gameview - hide all tool entities and textures with a single click (Menubar > View > Toggle > Game View)

Fake Sun Preview - toggle custom sunlight shader (Menubar > Renderer > Render Method > Fake Sun Preview)

Fog - toggle fog (requires custom sunlight shader to be active)

Filmtweaks - toggle filmtweaks

BSP/World - toggle d3dbsp and radiants world (only visible when a bsp is loaded)

Settings - opens either advanced sunlight, filmtweaks, effects or d3dbsp settings

Effects Editor - open effects editor for the currently selected fx_origin entity

Cubic Clipping - reduce drawing distance. Distance can be adjusted under Menubar > Renderer > Cubic Scale

Undock Window - triangle that appears on the upper-left corner of a fully docked window. Single click shows tab bar. Click-drag to undock the window.