The question: the Model Viewer's Scroll Choreography — pin the element in a fixed, transparent, z-indexed layer and drive its position, scale, rotation and opacity from the page scroll via keyframes, with an opt-in authoring guide — turned out to be the exact "kage-style" foreground effect people wanted for flat images, not just 3D models. So we ported the engine to a new image element. That raised three placement/shape decisions: (1) it's self-contained (its own runtime, no hard Animation-Engine dependency) and its closest structural sibling (Parallax Scene) lives in the shortcodes extension — so does it go there, or in the Animation Engine next to Model Viewer, its closest conceptual sibling? (2) Is "Scroll Choreography" the right element name, or should it be qualified? (3) The standard builder adds Styling / Animation / Advanced tabs only when a shortcode opts in — which of them make sense here?