Yes I found a solution, but it was not using this.
I used one of the REQ attributes (name was not one of them), and it worked…
Capella Studio refrain from cheking the “Label” tab, whenever the feature inserted is missing it seems. it worked even without the LineSemantic part.
By the way, what is this “lineSemantic” part? I searched a bit over the internet and over the a simple Capella metamodel, and would not find.