Thanks for your response. Yes, I’m aware of the problems of creating a new listing without login, but at the moment it seems, the login is a barrier for many interested people.
A new form or a known user account (like a dummy-user with open password) could also be a workaround. I have to chance the listing to a system user to avoid chances from other people. Both are not the perfect solutions, I know but I think I’ll try . Thanks!