Since: 25.01
Floating windows in niri always show on top of the tiled windows. The floating layout does not scroll. Each workspace/monitor has its own floating layout, just like each workspace/monitor has its own tiling layout.
New windows will automatically float if they have a parent (e.g. dialogs) or if they are fixed size (e.g. splash screens).
To change a window between floating and tiling, you can use the toggle-window-floating bind or right click while dragging/moving the window.
You can also use the open-floating true/false window rule to either force a window to open as floating, or to disable the automatic floating logic.
Use switch-focus-between-floating-and-tiling to switch the focus between the two layouts.
When focused on the floating layout, binds (like focus-column-right) will operate on the floating window.
You can precisely position a floating window with a command like niri msg action move-floating-window -x 100 -y 200.