For example, can oXygen be configured so that whenever an author inserts the <foo> element, that a <p> element is automatically inserted as a child element?

If so, what is the mechanism and can someone point me to the appropriate place in the oXygen documentation?

In this case, the DTD requires that <foo> have at least one child element, but the list of elements permitted by the content model is long.

I'd like to prevent authors encountering a warning that they won't easily understand, such as the following: