Share environment variables from pipeline to downstream job - maven

Question

I have two Maven projects in Jenkins, which download source code and then build, using mvn clean install and a pipeline that combines these two steps in a build stage.
The Jenkins maven plugin, expects to find an environment variable for the location of the maven repository. Namely, ${env.MAVEN_REPO}.
My goal is to define this variable in the pipeline and so that downstream maven build jobs use it.
This is my pipeline:
pipeline {
agent any
environment {
MAVEN_REPO = "C:\\Users\\Chris\\development\\repositories\\maven"
}
stages {
stage('Build') {
steps {
echo MAVEN_REPO
echo env.MAVEN_REPO
echo "${env.MAVEN_REPO}"
build job: 'projectA'
build job: 'projectB'
}
}
}
}
All three echo's above, print the already set value.
Now, in the downstream job, I have created "pre step > Execute Windows batch command", which contains:
echo MAVEN_REPO is %MAVEN_REPO%
echo List of variables:
SET
The problem is that MAVEN_REPO variable does not have a value.
Finally, printing all environment variables simply verifies that no MAVEN_REPO variable is defined.
I have even trying supplying the variable as job parameter, like so:
pipeline {
agent any
environment {
MAVEN_REPO = "C:\\Users\\Chris\\development\\repositories\\maven"
}
stages {
stage('Build') {
steps {
echo MAVEN_REPO
echo env.MAVEN_REPO
echo "${env.MAVEN_REPO}"
build job: 'projectA', parameters: [[$class: 'StringParameterValue', name: 'MAVEN_REPO', value: 'C:\\Users\\Chris\\development\\repositories\\maven']]
build job: 'projectB'
}
}
}
}
but still the variable does not have a value when trying to print it using the downstream job's pre-step phase and running this bat command echo MAVEN_REPO is %MAVEN_REPO%.
Note: My Jenkins instance currently runs on Windows 10.