>I believe we don't currently do any custom configuration...

See https://github.com/spring-projects/spring-xd/blob/master/spring-xd-dirt/src/main/resources/META-INF/spring-xd/plugins/common/spel-property-accessors.xml

Even if you don't need them for this use case, we should probably be consistent so that any function/accessor added is automatically available everywhere.