Jenkins local EnvVars with hudson function

Question

I try tofigure out how environment variable in jenkins are working and I get confused. Maybe someone can help to find my missunderstanding:

Pipleline:

import hudson.EnvVars;
import hudson.slaves.EnvironmentVariablesNodeProperty;
import hudson.slaves.NodeProperty;
import hudson.slaves.NodePropertyDescriptor;
import hudson.util.DescribableList;
import jenkins.model.Jenkins;
public createGlobalEnvironmentVariables(String key, String value){

       Jenkins instance = Jenkins.getInstance();
 
       DescribableList<NodeProperty<?>, NodePropertyDescriptor> globalNodeProperties = instance.getGlobalNodeProperties();
       List<EnvironmentVariablesNodeProperty> envVarsNodePropertyList = globalNodeProperties.getAll(EnvironmentVariablesNodeProperty.class);
 
       EnvironmentVariablesNodeProperty newEnvVarsNodeProperty = null;
       EnvVars envVars = null;
 
       if ( envVarsNodePropertyList == null || envVarsNodePropertyList.size() == 0 ) {
           newEnvVarsNodeProperty = new hudson.slaves.EnvironmentVariablesNodeProperty();
           globalNodeProperties.add(newEnvVarsNodeProperty);
           envVars = newEnvVarsNodeProperty.getEnvVars();           
       } else {
           //We do have a envVars List           
           envVars = envVarsNodePropertyList.get(0).getEnvVars();
       }
       envVars.put(key, value)
       envVars.override("HELM_CHART_NAME", "humpty")

       instance.save()
}
pipeline{
agent {
  kubernetes {
    yaml """\
      apiVersion: v1
      kind: Pod
      metadata:
        labels:
          pipeline: deploy
      spec:
        containers:
        - name: maven
          image: maven:3.5.4-openjdk11
          imagePullPolicy: Always 
          command:
          - cat
          tty: true
      """.stripIndent()
  }
}
environment{
    HELM_CHART_NAME = "foo"
}
stage('Build'){
  agent { label 'agentx'}
  steps {
    script {
      createGlobalEnvironmentVariables("HELM_CHART_NAME1", "test")
      //ANCHOR1
      echo "${HELM_CHART_NAME1}"
      echo "${HELM_CHART_NAME}"
    }
    timestamps {
      withMaven(jdk: 'JDK11.0.8_10', maven: 'apache-maven-3.5.4', mavenLocalRepo: 'mvn.repo', mavenOpts: '-Xrs -Xmx1024m -Xss1m', publisherStrategy: 'EXPLICIT') {
        sh label: 'Build', script: '''
          #ANCHOR2
          echo ${HELM_CHART_NAME1}
          echo ${HELM_CHART_NAME}
        '''
      }
    }
  }
}
}

If I add a new global variable with

createGlobalEnvironmentVariables("HELM_CHART_NAME1", "test")

Evrything works fine. But if I try to change an existing environment variable, that I define inside the global environment block, it will not change anything. At ANCHOR 1 I get

09:38:13  + echo test
09:38:13  + echo foo

At ANCHOR 2 I get the same

What s my flaw in to change an existing (global defned) environment variable?

envVars.override("HELM_CHART_NAME", "humpty")

From what I read is ,that override is the method to change existing and put is for create new one. put works, override not.

If I add a sh 'printenv' the output show me both environment variables but also HELM_CHART_NAME as still "foo"

The only thing that I think is that my hudson function only read global and not local environment variables? But how to access those locals defined in "environment{}" block?