If I’m understanding correctly, this sounds like an anchor menu: https://support.wix.com/en/article/editor-x-adding-and-using-anchors
You would have different sections or elements as the anchors and then the anchor menu will show were you are while scrolling up and down. It would work on mobile too if you use a complementary design that doesn’t clash with the page.
Note that linking to an anchor is a feature request at the moment if that’s something your client needed for this project.