I clicked the X on the details section on the right hand side of the screen and then, when realizing i needed it, I tried to leave and rejoin UEFN. This did not restore it, and now I do not know how to get it back. Help!
You see in the Window → Details menu you can have multiple Details Menus?
If you want to work with the details of 2 things at the same time, bring up an extra details menu and click the ‘lock’ button to lock it on current selection.