How to run multiple stages on the same node with declarative Jenkins pipeline?

Since version 1.3 of Declarative Pipeline plugin, this is officially supported.It's officially called "Sequential Stages".

pipeline {    agent none    stages {        stage("check code style") {            agent {                docker "code-style-check-image"            }            steps {                sh "./check-code-style.sh"            }        }        stage("build and test the project") {            agent {                docker "build-tools-image"            }            stages {               stage("build") {                   steps {                       sh "./build.sh"                   }               }               stage("test") {                   steps {                       sh "./test.sh"                   }               }            }        }    }}

Official announcement here: https://jenkins.io/blog/2018/07/02/whats-new-declarative-piepline-13x-sequential-stages/

You could define stages inside a script block. Those stages are kind of sub-stages of a parent stage running in a given agent. That was the approach that I had to use in a similar use case than yours.

#!groovywindowsNode = 'windows'pipeline {  agent none  stages {    stage('Stage A') {      agent {        label windowsNode      }      steps {        script {          stage('Stage 1') {                    windowsNode = NODE_NAME            echo "windowsNode: $windowsNode, NODE_NAME: $NODE_NAME"          }          stage('Stage 2') {            echo "windowsNode: $windowsNode, NODE_NAME: $NODE_NAME"          }        }      }    }  }}

I have found that this works as you would expect

#!groovywindowsNode = 'windows'pipeline {    agent none    stages {        stage('Stage 1') {            steps {                node(windowsNode) {                    script {                        // all subsequent steps should be run on the same windows node                        windowsNode = NODE_NAME                    }                    echo "windowsNode: $windowsNode, NODE_NAME: $NODE_NAME"                }            }        }        stage('Stage 2') {            steps {                node(windowsNode) {                    echo "windowsNode: $windowsNode, NODE_NAME: $NODE_NAME"                }            }        }    }}