Hello,

Thank you for submitting this request.There is an existing feature request for adding the ability to upload multiple files with the ImageBrowser. Currently this is not supported and by design only a single file can be uploaded at a time. While it is possible to configure the Upload to allow selection of multiple files after the Editor has been initialized, it results in undesirable behavior, thus a proper implementation of this functionality is required in order to avoid this.   

Regards,
Ivan Danchev
Progress Telerik