title: Separator with Jenkins parameters with declarative pipeline
body: <p>I have 50 parameters in my declarative jenkins pipeline, and it would be great to be able to make groups with separator.</p>
  
  <p>I saw this plugin: <a href="https://wiki.jenkins.io/display/JENKINS/Parameter+Separator+Plugin" rel="nofollow noreferrer">https://wiki.jenkins.io/display/JENKINS/Parameter+Separator+Plugin</a></p>
  
  <p>but it only does it with GUI, and I need to declare it in code, is it possible ?
  EDIT: Here is the code:
  I have only put 8 fields to be shorter, but 8 or 50, it should be the same</p>
  
  <pre><code>#!/bin/groovy
  
  pipeline {
      agent { label 'ansible24' }
  
      parameters {
          // init script params
          string(name: 'NAME', defaultValue: 'Nightly Valid', description: '')
          string(name: 'CODE', defaultValue: 'NIGHTLY', description: '')
          string(name: 'VERSION', defaultValue: '1.0.0', description: ' ')
          string(name: 'URL', defaultValue: "https://my.gitlab.net/config-daily.git", description: '')
          // What I need is programmatically add a separator like:
          // addSeparator()
          string(name: 'ADMIN_MAIL', defaultValue: 'mail@as.com', description: '')
          string(name: 'PUBLIC_DOMAIN', defaultValue: 'domain.com', description: '')
          string(name: 'PROVIDER', defaultValue: 'rhone', description: ' Define target virtualization provider. values : rhone, no-infra (read carefully use case)')
          choice(name: 'BASTION_STATE', choices: "present\nabsent", description: "Bastion state ")
      }
  
      stages {
          stage("Run Init script") {
              steps {
                  script {
                      def filename = "${WORKSPACE}/${params.CODE}/configuration.yml"
                      def yaml = readYaml file: filename
  
                      // General data
                      yaml.global.name = "${params.NAME}".toString()
                      yaml.global.code = "${params.CODE}".toString()
                      yaml.global.admin_mail = "${params.ADMIN_MAIL}".toString()
                      yaml.global.public_domain = "${params.PUBLIC_DOMAIN}".toString()
                      yaml.global.provider = "${params.PROVIDER}".toString()
                      yaml.global.bastion.state = "${params.BASTION_STATE}"
                      sh "rm $filename"
  
                      writeYaml file: filename, data: yaml
                  }
              }
          }
      }
  }
  </code></pre>