If the title sounds like I've made yet another barely useable app, it's wrong. This is what you can do with Developer Center in Sitecore:

1. Start Developer Center
2. Close all portlets / pages
3. Add Content Explorer (View -> Content Explorer). You might also choose to dock it according to your preferences.
4. [optional] Open any number of Content Editors for items by double clicking on them in Content Explorer. Could be useful as a start items, if you edit them often but adds startup time.
5. Window -> Save Workspace.
6. Ta-da: next time you need it, open Developer Center and choose Window -> Restore Workspace. Use Content Explorer to open additional tabs, for any items in any of the databases:

Fineprint: Cross database editing is not 100% perfect - some things will still work as if you haven't switched the database.

How to add a custom button to Sitecore rich text editor (Html Editor). Soon to be available as an article on SDN5.

Buttons displayed in the html editor tool bars are determined by the editor profiles. However a 'click' in 'html editor button' item contains a button name that is recognizable by the Cutesoft editor, and not the actual client side command to execute. So two steps should be made to properly add a new button to the html editor toolbar...