Retrieve content from a specified content block in Content Builder

ContentBlockByKey(1, 2, 3, 4)

1stringRequiredExternal key for content block
2stringImpression region for content
3BooleanIndicates whether a call proceeds if it fails to retrieve content. A value of true returns an exception and terminates the call. A value of false allows the call to proceed.
4stringDefault content to display if the call does not return content from the specified content area