How delete a relation without the form

[Raynald]

I deleted from a page a relation (this relation was not connected to any table) but at the famous question if I want to delete it completly I respond no by error

Now, I cannot generate my DDL because I have an error with this relation because, of course, it not connected to any table

So, How Can I delete this relation ? I don't see it anywhere

Thanks in advance and excuse my bad english