You are directly editting the JMD file instead of using the Central Control User Interface? Doesn't that version support the UI?
There is no capability that I'm aware of that is built into Central to do what you want to do. Central's job definition is straightforward so that it runs every task that is defined (unless one errors that is set up to stop the job if it errors). There is no "if/else" capability.
I believe that to do what you want would require two separate jobs defined with one running the extra program and the other not running it. Then the source of the files would have to have the intelligence to build the files to reference the correct job definition.
If you have no control over the source of the files then you would need to write your own program to run after the print step. This program would check the printer definition and if it was "mc001" it would do nothing and allow the next step (defined as a task that runs "/tmp/test.sh") and if it was not that printer it would tell Central to terminate the job by using the non-zero exit value or a properly crafted "jetform.rsp" file. (This is what I would do on a Windows system - I don't know if the same capability is present on your version of Central.)
If "/tmp/test.sh" is a program you wrote and you can modify it then you could have it check the printer parameter and either do its job or not. Then it could always run.
I'm aware I am coming into this discussion 4 years too late, but for anyone else who stumbles on this...
It is possible to run another task once the print has been done - you define this in the task and job sections, not the printer section
You need to define a new task, and reference the full path towards the executable
Then in the job table, add a step after the JFMERGE task (or your custom equivalent) that references the task created above.