How to export Cucumber Reports via Jenkins Pipeline
Working off what @chupasaurus said, here's what I came up with:

node('master') {
    dir("../builds/${BUILD_NUMBER}/") {
        sh "cp -r cucumber-html-reports $WORKSPACE"
    }

    archive "cucumber-html-reports/*"
}


Obviously all this does is archive the report for that build, but you can easily extend this to copy it somewhere else where it can be hosted or manipulated. Just make sure you put this after the Cucumber Reports plugin step.