If this is checked, and a folder is selected to move unrenamable files to, files that could not be renamed will be moved to this folder. It will only move files of the chosen extension.
If you load the source file names by selecting a folder and its subfolders, and the folder / subfolders contain files that are not the same as the extension type you are working with, those files will not be moved.
After clicking on this button you will be asked to provide a destination folder to move the unrenamable to.
This read only text box displays the folder to move unrenamable files to as chosen by the Select unrenamable files folder.
This read only text box displays the base destination folder chosen with the 'Choose destination folder' button.
