I'm using GNOME 3.28.2 on Ubuntu 18.04.4.
With the keyboard shortcuts "Special" + "Left Arrow", I can move the current window to the left, and resize it to half the screen; with "Right Arrow", the same, but to the right. A vertical split of the screen is created
With "Up Arrow", the window is resized to full screen. I would like instead to move it to the upper half of the screen. In other words, I would like to obtain a horizontal split of the screen, similar to the vertical split which is obtained with "Left" and "Right Arrow".
Is it possible? How?
https://gitlab.gnome.org/GNOME/mutter/issues/579 shows it's a requested feature not yet implemented directly in GNOME3.
However, there's an extension for GNOME, gTile, which gets you there, as illustrated in https://www.addictivetips.com/ubuntu-linux-tips/tiling-windows-in-gnome-shell/ with its Manual Tiling option. Switch to an app then manually redraw its tile for its horizontal slice (top or bottom). Switch to another app, and manually redraw its tile. gTile looks at the grid drawing and scales apps accordingly.
tilingnome also allows you do do this and also offers horizontal layouts.