Open new editor pane in workspace (handle is missing) There are a few tutorials (for example this one, screen shots below) which show you can add a new pane to a workspace but in my version of Blender 2.8 (running on Windows 10) I can't recreate this option.  It looks like the handle is missing.  The handle being the little diagonal lines in the top right corner.
It appears that the UI is different?  You can create a new editor pane inside a workspace by clicking and dragging in the tiny dark space between the panes.  See annotated screenshot below.