My issues with the current interface are that
- The 'screen options' tab thing isn't that discoverable visually;
- It isn't clear what 'screen options' refer to (in a CMS that manages what users will eventually see on a monitor of some kind, it could mean anything)
- It isn't absolutely clear the controls affect the current interface rather than, say, the page which is eventually presented to a reader.
- It's not possible to discover what benefits there are to using the 'screen options' controls until one opens it.
I think we could resolve all three of these issues by embedding these controls within the UI. The simplest way to do that is to control which sidebar panels are shown not with a set of tickboxes, but with expandable / contractable elements.
download bmml source – Wireframes created with Balsamiq Mockups
Now I don't need to spot and open the 'screen options' control to realize I can open an 'excerpt' editor. And it's obvious that these controls affect my current UI rather than the kinds of content that get presented to the reader.
You can now also add drag-and-drop reordering to further help editors manage their workspaces.