PaperWM is a Gnome Shell extension which provides scrollable tiling of windows and per monitor workspaces. It's inspired by paper notebooks and tiling window managers.

Windows are arranged in columns on an infinite strip going to the right.
Opening a new window never causes existing windows to resize.

Every monitor has its own separate window strip.
Windows can never "overflow" onto an adjacent monitor.

Since windows go left-to-right horizontally, workspaces are arranged vertically.
Every monitor has an independent set of workspaces, and there's always one empty workspace present all the way down.

All these scrolling WM:s sound so fun! I want to try one one day.