Can i create & attach a component inside a component ?

Yes.

If memory serves, UE warns you when the editor starts and some hard coded ref in a constructor can’t be found.
I never had any warning here, and everything appears fine when creating a new BP.

Anyway, just in case, i remade the hard links (right click / copy reference, then paste, no possible error), and i get the same behavior.

I’ll go on with more testing, like trying with a brand new project, etc. Something might be corrupted in my current project.

The code is so simple that the error may be somewhere else, configuration, corrupted mesh, etc…

Cedric