4. Details / Preview Settings
The Details panel, which is similar to the Main Editor, is primarily used for modifying the properties of added elements like Sockets.
For example, when you add a Socket to the Skeleton, clicking on the Socket in the Skeleton Tree will populate the Details panel with options related to how the Socket functions.
Also located in this section is a tab for Preview Settings which enable the ability to define the viewport settings such as the Animation Mode or Animation to use as a preview, switch Skeletal Meshes that are used for the preview, as well as viewport lighting and Post Process settings applied so you can preview your settings with various lighting applied.