Hey _Val_,
ah ok, I missed the information about the clish commands. I looked at the commands and information in the operations mode section (limiting the execution of a deployment plan file) of the admin guide, which states:
2. When you generate the Installation Candidates List File, specify the Filter File:
./CentralDeploymentTool -generate -candidates=<Path to and Name of Installation Candidates List File>.csv -deploymentplan=<Path to and Name of Deployment Plan File>.xml -filter=<Path to and Name of Filter File>
3. When you run the Deployment Plan File, specify the Filter File:
./CentralDeploymentTool -execute -candidates=<Path to and Name of Installation Candidates List File>.csv -deploymentplan=<Path to and Name of Deployment Plan File>.xml -filter=<Path to and Name of Filter File>
The workflow is clearer in your code example, but it seems that you can use the filter in both commands in the CLI and you can decide where to filter the the gateways for execution.
I hope it became clear why I asked the question when to use the filter argument.