I've been using Ubuntu 16.04 and there was a feature in the Unity Launcher: when mouse hovered to the top and bottom, the Launcher would move (slide) icons up and down respectively. It's not happening in the Ubuntu Dock after I upgraded to Ubuntu 20.04 and I am facing a lot of trouble when multiple apps are opened, and trying to switch between them.
Ubuntu 16.04 Launcher feature explanation:
If you open more applications than can be shown in the Launcher, the Launcher will “fold” the application icons at the bottom of the Launcher. By Simply moving the mouse to the bottom of the Launcher,the Launcher icons “slide” and the folded application icons unfold for easy access.