You add and remove ESXi hosts to a vSphere Trust Authority Cluster by using VMware-supplied scripts.
In vSphere 7.0, you add and remove ESXi hosts to and from an existing vSphere Trust Authority Cluster or a Trusted Cluster by using VMware-supplied scripts. Starting in vSphere 7.0 Update 1, you use the remediate function to add ESXi hosts to an existing Trusted Cluster. See Add a Host to a Trusted Cluster with the vSphere Client and Add a Host to a Trusted Cluster with the CLI. In vSphere 7.0 Update 1, you still must use scripts to add ESXi hosts to an existing Trust Authority Cluster. See the VMware knowledge base articles at https://kb.vmware.com/s/article/77234 and https://kb.vmware.com/s/article/77146.