I am using Blender 2.8 (Windows 10). I have now been able to create two editor panes in the same workspace (see this Q/A). The new editor pane(s) is set to the same editor type as the existing pane. Trying to change one pane's editor type changes the other pane's editor type. How can you set them to different editor types? A tutorial suggestions this is possible (screenshots attached).
Editor panes in my blender seem to be locked to be of the same type. Changing one type changes the other's type to the same type: