How Do I Upload Multiple Files to S3?

Multiple files can be read via the Filepicker widget at a time. If say you have 5 files read by the Filepicker widget then you can create a submit button and configure the onClick event to iterate from 0 to 4 i.e. indexes for the files in the Filepicker widget and invoke your upload query like
upload_query.run({ file: FilePicker1.files[i] })

In the upload query, you can reference the ith file like:
{{ this.params.file.data }}

You can check our docs on query.run() and uploading files to S3 to learn more.