Same question - internet search indicates body in DELETE call is a bit of a gray area (rest - Is an entity body allowed for an HTTP DELETE request? - Stack Overflow ). i have a DELETE call Dev provided for testing that sends a body (able to do with Postman, but Content tab of REST step is disabled, causing the automation to fail)
I guess Scripted Assertion + Beanshell is the next option...
URL urlDeleteURL = new URL(DeleteURL);
HttpURLConnection connDeleteURL = (HttpURLConnection) urlDeleteURL.openConnection();
connDeleteURL.setRequestMethod("DELETE");