It is not possible to apply the overlay below the scroll and the overlay whose overlay location depends on page scrolling.
I hope you can improve it.
Yes, this is the way the Overlay feature works currently. You cannot apply it below the scroll. Use this link Overlays below the viewport height in scrollable artboards – Adobe XD Feedback : Feature Requests & ... to vote for this feature as also provide suggestions.
if i may, that is a bug, not a feature.
just like adding an element below viewport hight would be unconcievable.
This is exactly my problem
I'm glad to see, that after three years Adobe on are on the case 😛