4. Details / Preview Scene Settings
The Details panel, which is similar to the Main Editor, is primarily used for modifying options that have been added while working in the Asset Editor.
For example, when you add a notify to an Animation Sequence, clicking on the notify will populate the Details panel with options related to the notify. Adding a new section to an Animation Montage, you can modify the content of the section from the Details panel.
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.