How to make an non extensible EClass (from an addon).. extensible?

I would very grateful if you could show me how to resolve the following issue:

So I was coding a .vptext file in Capella Studio and obtained the error message below:

The EClass Requirement[Requirements,] is not defined as extensible.
Extension defined by MyNewClass in MyNewVP viewpoint specification

How is it possible to make the Eclass extensible? Especially and particularity the “Capella Requirement” classes (Extends Requirements.requirement)


Please refer to this message for an answer from the Capella Studio point of view.

As far as possible please avoid to duplicate your questions, this is second time I write this kind of message today.