The Quick Tile Window keyboard shortcut Super+Arrow left makes the window in focus occupy the left half of the screen. Super+Arrow right makes the focused window occupy the right half.
By using these two shortcuts, two windows occupy space in a 1:1 ratio.
How can I modify these shortcuts to have the left window occupy 45% and the right window 55%?
I couldn't find an easy solution in the basic linux settings.
But there is a Project on GitHub: https://github.com/pkkid/pygrid
While its not the setting you described, you may find this extension helpful: https://extensions.gnome.org/extension/28/gtile/
With this you can tile windows to 12.5% screen columns (like 62.5 - 37.5)