Оригинален текст - Swedish - Välkommen till världen lilla vän!

I don't find any verb

I think we can consider it an ellipsis of:
"Vara välkomna...!", can't we?

CC: Bamsa lenab

Yes Lilian, you are absolutely right!
This is a very common phrase when a child is born.

Thanks Lena, so I'll release the request, OK?

CC: Bamsa

Yes, I think so!