This extension shows you view once media in the browser, so you can save or view it as many times as you want.
You need to log out and log back in from WhatsApp Web (rescan the QR code) every time you want to access a new view once media.
With recent updates, the chances of recovering previously opened media are very low. It is recommended that you do not open the media on your cell phone for the extension to work properly.
To activate the extension, you need to subscribe for R$1.99 per month.
This amount is what keeps the developer fighting against all of WhatsApp's attempts to take away access to view once media.