I know this is an older post. I just want to reply so that the others do not have to search.
As mentioned in this post:
https://forum.centos-webpanel.com/informations/cwppro-reviews/msg17701/#msg17701there is no more button specially for pro users. Storage backend "Malloc" is the feature that we look for.
I also found that if you call "..../admin/index.php?module=varnish_conf"
instead varnish_conf
2 you see an option "Varnish Disk Storage Size (recommended: 1G):"
I did not tried yet and even wont. Could someone tell me if that is deprecated/replaced with Storage backend "File"?