There's a problem with the use of the standard Windows file selector and folder selector, which the Exclude options' Add function uses. They have certain restriction built into them - certain files and folders that are never displayed or selectable.
For example, I was trying to add hyberfil.sys and pagefile.sys to my exclude list - they can never be fixed, so why should Defraggler list them each time? However, the Windows file selector dialog refuses to display them. Even if I go to C:\ and manually type in 'pagefile.sys' as the filename, it refuses to select it because it is 'being used'.
Also, I wanted to exclude the cache folders of my browser - since any given cache file has a lifetime /far/ shorter than the interval between defrags, there's not much point to making them contiguous. (Now, if there were an option to move them all to the end of the disk, so they didn't create holes when they were, inevitably, deleted...) They are in C:\Users\Jordan\AppData\Local\Mozilla\Firefox\Profiles\${ProfileName}\Cache. However, you simply cannot get there in the Windows folder selector dialog. If I navigate to C:\Users\Jordan, AppData\ simply isn't displayed as a subfolder.
Now, obviously these cannot be considered bugs in Defraggler. The bug in Defraggler is that the textboxes int the Options->Exclude->Add are not editable. You cannot type into them directly and enter a file or folder name manually. You have to select a filename through the Browse button, which means you cannot work around Windows' 'User equals ID ten plus'* restrictions.
Either the textboxes need to be writable, or the Browse button need to use a custom dialog box that allows you to view and select hidden files or folders, or whatever library provides the default dialogs needs to be given whatever option relaxes those restrictions (assuming there is one).
* "User = ID10+"