Chapter 1.1 UDK Editor: Level Editor

Unreal  Editor and UI Tools 

Unreal Engine 3 contains a suite of tools used to create and edit levels, import and organize art assets, create specialized content assets, and much more. The cornerstone of these tools is Unreal Editor, or UnrealEd. Unreal Editor is comprised of a Level Editor, a collection of Browsers, and a set of specialized Editing Tools.
http://udn.epicgames.com/Three/EditorAndToolsHome.html

Unreal User Interface Guide
UnrealEd is a suite of tools for working with content in the Unreal Engine. At the core, it is used for level design; but contained within are editors and browsers for importing and manipulating content for your game project. This section will focus on the level editing capabilities of UnrealEd, the Browser and Editor Tools will be covered in depth in the subsequent sections of this Chapter.
http://udn.epicgames.com/Three/UnrealEdUserGuide.html

Main Editor

Main Editor MenuBar    http://udn.epicgames.com/Three/MainEditorMenuBar.html 

*Update -   "Play" and  "Preferences" now have their own drop down Menu

Main Editor ToolBar     http://udn.epicgames.com/Three/MainEditorToolbar.html
*Updates - "Mobile" Authoring Support (Emulator, Previewer, etc ) & "Kismet Debugging" Tools added

Main Editor ToolBox    http://udn.epicgames.com/Three/MainEditorToolbox.html

*Update - New Editor Modes: "Landscape" Mode and "Foliage" Mode 

Landscape Mode   http://udn.epicgames.com/Three/LandscapeEditing.html#Landscape%20Edit%20Mode

Foliage Mode         http://udn.epicgames.com/Three/Foliage.html#Foliage%20Edit%20Mode

Viewports

ViewportToolbar     http://udn.epicgames.com/Three/ViewportToolbar.html

• Show Flags - rendering options which can be enabled and disabled independently. A viewport can have any combination of show flags enabled. In the editor, the show flags are modified using the dropdown button on the viewport's toolbar. In the game, show flags can be toggled using the show command.            

http://udn.epicgames.com/Three/ShowFlags.html 

• View Modes -  mutually exclusive rendering styles. A viewport can only have a single active view mode. In the editor, the view mode is selected using the associated buttons in the viewport's toolbar. In the game, the view mode can be changed using the viewmode console command.           

http://udn.epicgames.com/Three/ViewModes.html

Status Bar

The Console Bar provide SCC Integration stats and World Constraint Settings for Grid, Snap, Rotation, DrawScale, and Auto Save.
http://castovocaludk.blogspot.com/2011/07/status-menu-icons.html

Additional Tools

UI Controls

Mouse & Keyboard Controls 
http://udn.epicgames.com/Three/EditorButtons.html#Basic%20Editor%20Usage
Hot Keys Shortcut Sheet
http://udn.epicgames.com/Three/rsrc/Three/EditorButtons/UE3_Shortcuts.doc

Property Window

The Property Window, used in many places in various editors, is where variables exposed by script can be edited. These interfaces will be use to manipulate the various attributes defining an Actor.
http://udn.epicgames.com/Three/PropertyWindow.html

Play in Editor

Play In Editor (PIE) is a useful tool to quickly preview gameplay in a level while editing.
http://udn.epicgames.com/Three/PlayInEditor.html

Working with Level
With this Chapter complete we can now move on to placing actors, selecting actors, transforming actors,  and modifying actors - the basic methods used to create a level in Unreal.The following walkthrough will familiarize the reader with the tools use to manipulate actors:
http://udn.epicgames.com/Three/UnrealEdUserGuide.html#Working%20with%20Levels