Follow-up since the question has not been marked by the OP as answered.
EDI transaction formats follow an industry standard so the format of the actual EDI input transaction should follow that standard. A partial sample of what an EDI transaction might look like is:
ISA*00* *00* *ZZ*MEDDATA *ZZ*MEDDATA ....~
To get the above into an input request that DevTest can recognize, you need to know how the system under test is sending the data. Suppose for example that the EDI data is wrapped in an XML element as part of a Webservice or REST call.
You might need to use a Request Data Manager to marshal the EDI transaction value into the request body so it can be recognized by DevTest.
Assume for a moment that the R/R pairs contain the EDI transaction within a <Payload> element in the XML. For example,
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<s:Header>
<o:Security ....</o:Security>
</s:Header>
<s:Body>
....
<Payload xmlns="">ISA*00* *00* *ZZ*MEDDATA *ZZ*MEDDATA....</Payload>
....
</s:Body>
</s:Envelope>
In the above example, set up your R/R pairs according to the input format sent by the system under test.
Use one of the XML parsing DPHs (such as SOAP or XML) to create a request argument list.
ADD an RDM DPH and include an instruction to copy the 'Payload' element (Argument) value into the Request Body.
ADD the EDI DPH after the RDM DPH to parse the actual EDI transaction into the list of arguments.
Note: You can also use the RDM DPH to remove unwanted arguments if they are not required.