I believe this Hype demo project does what You want: test_JHSv1.hype.zip (864.7 KB)
I moved the “Ellipse” outside of the “scroll group” and had it match the movement of the “scroll group” when it first appears and slides up. The CSS is the same.
**Note:** Even though I left the CSS "position: sticky" in the "Head HTML" I do not think this CSS can be operational in Hype as "sticky" is a "hybrid" - "relatively" positioned until it hits a specified threshold at which point it becomes "fixed". Removing this CSS has no effect on the demo I did above as it does not rely on the CSS.