In the Manage Jenkins -> configure system panel, one can add a vSphere cloud.
After adding a vSphere cloud, one can add one or more slave templates.
There is no delete button to delete a slave template.
The only "delete" option available is to delete the entire vSphere cloud (login details and all templates together).

This is caused by the config.jelly file (src/main/resources/org/jenkinsci/plugins/vSphereCloud/config.jelly) using a <f:repeatable ...> element for the list of templates but not including a <f:repeatableDeleteButton ...> element within that.