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).
Ok this isn't possible. What's being show in the video is opening a different Editor Type which is possible. What the question is asking for is opening the same Editor Type but with a different Editor Mode. And this isn't possible: perhaps because the contextual interface on the right would be confusing as it would depend on which editor pane you were in.