The toolbar

Above the Viewport is the toolbar, as shown in the following screenshot: 

This gives access to some of the more commonly used features of the editor:

• Save Current: This saves the current level. Save on a frequent basis. By default, the editor has autosave turned on, but it's set to 10 minutes, and that can be a lot of work when you're in the zone.
• Source Control: This hooks your content to subversion, perforce, or Git content control. If your team uses one of these, this will save a lot of time over having to do this outside of the editor.
• Content: This opens the Content Browser if you have that tab closed.
• Marketplace: Pressing this may seem like it does nothing, but it opens the Marketplace in the Epic Games launcher. You'll need to switch over to that program to see it, as it doesn't automatically pop back up.
• Settings: This provides access to some settings menus we'll be talking about in a bit, along with a number of selection, quality level, and snap settings for the Viewport.
• Blueprints: This lets you create and find Blueprint classes, but this is easier done in the Content Browser. This is also where you access the level-specific Blueprint.
• Cinematics: This is beyond the scope of this guide, but here is where you would get started with creating cinematics at your level.
• Build: Here is where you set the rebuild options for the level, and where you rebuild geometry, lighting, and pathing in the level. For programmers, most of this is not our focus, but you will want to rebuild pathing when working with AI, and doing a complete rebuild by simply pressing the Build button in the toolbar will get rid of the red LIGHTING NEEDS TO BE REBUILT notification in the Viewport and in game. To make things quicker, keep the Lighting Quality at Preview until you're ready to do non-test builds.
• Play: This lets you play the current level without having to build the entire project. By default, this uses the current Viewport, but exiting from this with Esc doesn't reset the camera, so I usually set this to New Editor Window. For multiplayer testing, you can also set the number of players, which will open a separate window for each one. If you have compiled the engine yourself and set up dedicated server functionality, you can enable that here as well. At the bottom is a link to Advanced Settings, such as mouse control, Viewport sizes, and server options.
• Launch: If you are developing for mobile or browser, you can launch to those devices from here.