This option opens the Choose Columns dialog, where you configure the attributes that are shown as columns in the object list. Together with the objects names you can configure LEX to show any object attributes to be shown directly in the list as additional columns:
There are five important basic information for each object, which can be chosen directly to be shown as a list column or not. But with the More Option and the Choose Columns dialog, you can specify any attribute to be shown as a list column:
In the dialog, you see what attributes are currently shown as list columns, and you can choose additional ones from a list of attributes which are valid to the current directory according to the schema:
By the way: If you want remove all the object list columns except the basic attributes, just deactivate the More option in the menu: this cleans up your list columns quickly!
You could reach the More option also by opening the context menu of the object list column header - just right-click on the column header: