Thank you for your input! We will consider this functionality in upcoming releases if it will be popular.
Everyone, please continue voting for this feature if you consider it important.
— rkGareth commented
Sometimes when add a firewall rule you need to know why you added. Having the ability to add a comment would be great.
If you are editing iptables directly you can add comments to the file. Be nice if you could do it via the UI.
Since Plesk Onyx you will be able to install memcache as a Docker container and configure http(s) proxy rule for it to map to your web app.
Docker and proxy rules are available in Plesk Onyx Preview already, you can try it here https://talk.plesk.com/threads/plesk-onyx-preview-and-feedback.337172/
Need memcached in php7-fpm support in plesk.