Layout Field: Split right half of layout in half horizontally?

I’d like to create a layout with one column on the left taking up 50% of the layout’s width (and 100% of its height) and a horizontally split column on the right, also 50% in width. Like this…

Screenshot 2022-08-12 at 06.23.43

Is this possible?

No, the layout field supports columns only as you can see in the configuration. The only thing you can do is create a custom block with two sections.