Fedilab has two buttons in the “load more” thingy. One to load the contents above the fold (so you an keep scrolling up) and one to load the buttons below, so you can keep scrolling down. It works remarkably well.
I’m pretty sure this is hell to program, as most prebuilt list views will use a Y position measured from the top of content. This makes it hard to insert content in the center if you’re trying to scroll up, as you may not know the exact height of the content you’re loading to compensate for the change in position.
However, Fedilab solved it, so other applications can solve it too!