Can I change the primary key for identifying hosts in the SIEM app?

I'm shipping logs from a number of hosts via a single filebeat running on a collector. As a result, the default primary key used by the SIEM app host.name is not very useful to me. host.hostname would work a lot better. Can I change the primary key for identifying hosts in the SIEM app? Can I alternatively add/remove/change lines in my filebeat.yml to remap fields so that host.name will contain the same data as host.hostname?

Could I maybe work around this problem by using the copy_fields processor? I've tried something like this:

processors:
    - copy_fields:
        fields:
            - from: host.hostname
              to: host.name
        fail_on_error: false
        ignore_missing: true

But, I don't seem to get the desired result...

I haven't done this before as I particularly enjoy using host.name but this might be helpful as it looks like someone else has done this before: