Many users like to be able to clear out sessions from an agent gracefully, i.e. don't create any new sessions on it but let the existing ones stay. This is usually done in preparation for some service work being done on the agent.
Right now the method of doing this is removing it from /vsmserver/terminalservers. This is however a bit of a blunt tool as it in some ways makes the agent no longer part of the cluster (e.g. isn't shown in load info). It is also not very apparent that this is the way to do it.
We could consider making the process simpler somehow, e.g. by letting the admin specify "disabled" agents as a separate thing.