thank you for your answer.
I've attached a sample project with my custom editor (it is intended as a base class for more specilized editors and have a variable number of buttons).
As you can see in the EditorRequired event, the multiline flag for the editor in column1 is set to false and everything works fine, while the editor in column2 have multiline set to true and you can't edit the value.
I have one more question, as you can see from my code I've used a trick to defer the execution of the CreateChildElements() until the end of the class contructor (so I know how many buttons I need). Obviously I don't like my solution very much, so I'd like to know if there's a better way to do that.
Thank you very much
P.S.: I can attach only images so to send you the sample project I've changed the attachment extension from zip to jpg