Right (control) clicking in the editor allows the submenu to reveal “Layout Orientation > Horizontal | Vertical”. What is this?
Some languages (Japanese, Chinese) can be written from top to bottom, so this lets you change to that mode. It is part of the standard macOS text view context menu by default, but I don’t think it ever makes sense for a code editor. I will remove it!
(as a side note, I’m surprised that there’s not a right-to-left option in this menu for Arabic/Hebrew, but I guess that is more of a system option)