At design time, I'd like to set the value of a property on a document type that is not editable by users when they create content. So, all content created from that content type would get the same value -- the value that I set at design time.

It appeared to me that the built-in Label property editor might be what I was looking for, but I cannot figure out how to set the label's value via the backoffice.

Am I misunderstanding how the Label property editor is used?

Is there some other, preferable way for a developer to set a non-editable value against a document type?