In principle, this can already be done with a shell script step from a workflow (using, e.g., the ssh interface to gerrit), but that can be a bit tedious. But a feature that is not currently possible is to influence how the voting happens after the build finishes. See JENKINS-32692 for some background.
One solution on the Gerrit Trigger side, which would probably provide a better integration in the long run, would be to provide a workflow step that can be used to influence the final vote: e.g., to set the Url to Post option, or the message to write (this could also replace the ability to pass Unsuccessful Message File, which is not possible from a workflow).
I can create a separate issue for this if you prefer.