I don't think the exact feature you're describing exists at the moment, but the Current Folder browser does have a "Details" panel that you can use to preview the contents of a file. I believe it's minimized by default, but you can right click on a file and select "Show details" to expand it. For MATLAB scripts, the details will show all of the sections and sub-functions in the script, and from there you can double click on a section name to go to that section in the Editor.
This will only show you details for the one file that's selected in the current folder pane, not for all the files you currently have open in the Editor, but if you're spending most of your time working in the same directory it might still come in handy for you.
