I had the option to add the PowerShell plugin but I did not have the option to not install the Management Console or the Catalog Service.
Just checked it and I have to say you’re absolutely right - it looks like Veeam PowerShell, Management Console and Catalog Service can't be installed separately.
However, I’m wondering for what purpose you need to deploy snap-in only.
If you have a machine which is playing the role of VB&R server and you’re willing to execute PowerShell on that machine from your laptop, then there is no need to deploy Veeam PS snap-in, since all can be done by the means of remote PS execution.
Hope this helps.