LinkUploadURL
This option defines the URL to post files through the "Upload Tab" in the link dialog. It can point to the default file uploader:
FCKConfig.LinkUploadURL = FCKConfig.BasePath + 'filemanager/connectors/' + _QuickUploadLanguage + '/upload.' + _QuickUploadExtension ;
or any custom implementation of it:
FCKConfig.LinkUploadURL = '/myuploader/upload.php';