Like other tupane types, the popout details when a system is clicked on needs to have a "remove" option on it. (eg. see activation keys or orgs).
Added in 22b158650dbe49002209286ccdc393beae5f04ce
Verified with following katello build: [root@dhcp201-162 certs]# rpm -qa | grep katello katello-0.1.154-1.el6.noarch katello-trusted-ssl-cert-1.0-1.noarch katello-cli-common-0.1.30-1.el6.noarch katello-glue-pulp-0.1.154-1.el6.noarch katello-configure-0.1.46-1.el6.noarch katello-qpid-broker-key-pair-1.0-1.noarch katello-glue-candlepin-0.1.154-1.el6.noarch katello-all-0.1.154-1.el6.noarch katello-repos-0.1.4-1.el6.noarch katello-cli-0.1.30-1.el6.noarch katello-glue-foreman-0.1.154-1.el6.noarch katello-common-0.1.154-1.el6.noarch katello-certs-tools-1.0.1-1.el6.noarch katello-httpd-ssl-key-pair-1.0-1.noarch "Remove system" option is available now. Please see the attachment in next comment.
Created attachment 549184 [details] "Remove System" option under system details on top corner in right pane
getting rid of 6.0.0 version since that doesn't exist