Optional string in editor

Hello,

How to make a string as optinal in editor.

For example: I have in editor

interface abcd service {name} {

}  (and this concept is derived from Baseconcept and implements INamedConcept) where "service" is optional string.

I have tried with show-if property in inspector but it didn't really worked.

The goal is when the user start typing service, the projectional editor should accept only "service" otherwise it is empty.

Thanks alot for any suggestions