I have opened the improvement (http://jira.kaaproject.org/browse/KAA-647) to get ability to remove an arbitrary element of an array on Avro UI.
But recently I have faced with the case when an array of records has the 'Delete' button on Avro UI (see the screenshot).
So there is some inconsistency.
According to the screenshot there is one more issue. The 'Delete' button is partially invisible behind the scroll bar.