Check out this widget from the Mendix App Store called Dropzone. It allows you to drop or select files/images to upload.
Hi Nick, at this point it is not possible. You can file a feature request in our support portal if you would like this functionality to be included.
Please find the support portal here
Is multiple Upload features now available in Mendix? If yes, then how it can be done?
Use the Dropzone AppStore Widget if you have not yet figured out the solution