You want a list of files - the example gives a list of files.
As I said, you HAVE to do this from Node-RED, you are not permitted by any browser to mix information from a server and from the local machine. As the UI Dashboard is delivered by Node-RED (a server), you cannot then get the list of local files from the browser itself.
Here we are saying that you can get round the issue by running Node-RED on the same device as the browser and so you can get to the filing system on that device from Node-RED and send the information to the browser.
The example does the file list - it gets the data from the filing system via an operating system command. The next step would be to send that information through to the browser using Dashboard.
Please try the example before dismissing it.