Amazon S3 console: download multiple files at once

It is not possible through the AWS Console web user interface. But it's a very simple task if you install AWS CLI. You can check the installation and configuration steps on Installing in the AWS Command Line Interface

After that you go to the command line:

aws s3 cp --recursive s3://<bucket>/<folder> <local_folder> 

This will copy all the files from given S3 path to your given local path.

Selecting a bunch of files and clicking Actions->Open opened each in a browser tab, and they immediately started to download (6 at a time).