The file manager in Sitefinity 3.x is thin, and one missing feature crosses the line from annoying into dangerous. It does not prompt before a delete. One wrong click and the file is gone, no confirmation, no undo. For a tool non-technical editors live in every day, that is the kind of default that eventually costs someone a production asset and a bad afternoon.
The fix is to rebuild the page on top of the RadFileExplorer, which you already have because it ships with the controls. The page lives at ~/Sitefinity/Admin/Files.aspx, and at its core the change is as simple as dropping a RadFileExplorer onto it. That alone buys you the delete confirmation, a real browse experience, and upload handling that does not feel like a 2008 web form.
While I was in there I added a couple of things I always end up wanting anyway. Two textboxes that show the absolute and the relative URL of whatever file is selected, so you can grab a link without hand building the path. The aspx also lets you set the root folder and the default skin.
Point that root at a ~/files folder instead of the site root. An editor hunting for an image has no business being one misclick away from your core application files, and scoping the explorer to a dedicated folder keeps them in the part of the filesystem that is genuinely theirs to manage. It is a small boundary, and it heads off the entire category of conversation that starts with someone asking why the bin folder is empty.