Default service task I/O parameters not shown in "I/O Parameters" tab

Description of problem:
Service task has two default parameters:
"Parameter" - input of operation
"Result" - output of operation

"Parameter" and "Result" can be set on "Service Task" tab. But these assignments are not shown in "I/O Parameters" tab

Version-Release number of selected component (if applicable):
jbds-9.1.0.Beta2_jbdsis-9.0.0.Beta1
BPMN2 Modeler - 1.2.3.CR2-v20160209-2002

Steps to Reproduce:

1. Create process containing 'service task'
2. Set implementation for 'service task'
3. Set operation for 'service task'
4. On 'Service Task' tab set 'Source' for operation input
5. On 'Service Task' tab set 'Target' for operation output
6. Save your work and check 'I/O Parameters' tab

Actual results:
There will be not "Parameter" neither "Result" assignment

Expected results:
There will be "Parameter" and "Result" assignment

Additional info:
User can fill on "I/O Parameters" tab input assignment named "Parameter" and output assignment named "Result". These are also stored in xml source. But they disappear from "I/O Parameters" tab after properties are reopened.