I recently came across a very interesting discussion on the Oracle BPM forum which stimulated my interest for investigation; how to suppress the human task custom outcomes from the action bar in the BPM Workspace application in 12c!
When you deploy a BPM process or a BPEL service that includes a human task component, the BPM Workspace will automatically include in its action bar the custom outcomes that you have defined on your human task.
There are cases though that you might want to suppress this default behavior and not have your custom actions appearing in the actions list but just have them displayed in the task details.
In 11g this was "officially" supported with a checkbox option ("Show approval controls in task details only") in the advanced human task properties.
So go to your human task definition file (.task file), switch to source view and insert into the "preActionMandatoryUserSteps" element the following
Your human task definition should look like below.