Since you shift the reference from "Explorer" in the first sentance, to "Editor" in the second, it is unclear what is being asked here.
Is it that, when a particular class file is open in the Source Editor, you want the Explorer Filesystems pane to highlight the corresponding class node icon?
Or, if you click on the line that begins the class definition in the source file, the corresponding class node icon is highlighted (this for source files that may contain more than one class definition)?