Changing a Custom Composite Type

I have created a custom composite type in a configuration element to contain details of my vcenters to use in a template syncing orchestrator workflow I have, but now realise I need to add a new field to this type, I cant find where to do that. Is it possible?

For example my type consists of:

(VcenterName:string,DatacenterName:String,...) nut I want to add a new field of TemplateName:string