Run multiple Jobs in parallel via Jenkins Declarative pipeline syntax

Question

I want to execute multiple jobs from a single pipeline using declarative syntax in parallel. Can this be possible!! I know we can make a declarative parallel pipeline using "parallel" parameter.

pipeline {

    agent any
    parallel{
    stages {
        stage('Test1') {
            steps {
                sh 'pip install -r requirements.txt'
            }
        }
        
        stage('Test2') {
            steps {
                echo 'Stage 2'
                sh 'behave -f allure_behave.formatter:AllureFormatter -o allure-results features/scenarios/**/*.feature'
            }
        }
        
        stage('Test3') {
           steps {
                script {
                    allure([
                        includeProperties: false,
                        jdk: '',
                        properties: [],
                        reportBuildPolicy: 'ALWAYS',
                        results: [[path: 'allure-results']]
                    ])
                }
            }
        }
    }
    }
}

Below image will show you the proper flow that I want. Any approach how to do it?

Answer 1

// Pipeline project: SO-69680107-1-parallel-downstream-jobs
pipeline {
    agent any
    stages {
        stage('Clean Workspace') {
            steps {
                cleanWs()
            }
        }
        stage('Parallel stage') {
            parallel {
                stage('Stage 2') {
                    steps {
                        build 'SO-69680107-2'
                        copyFiles( "$WORKSPACE\\..\\SO-69680107-2", "$WORKSPACE")
                    }
                }
                stage('Stage 3') {
                    steps {
                        build 'SO-69680107-3'
                        copyFiles( "$WORKSPACE\\..\\SO-69680107-3", "$WORKSPACE")
                    }
                }
                stage('Stage k') {
                    steps {
                        build 'SO-69680107-k'
                        copyFiles( "$WORKSPACE\\..\\SO-69680107-k", "$WORKSPACE")
                    }
                }
            } // parallel
        }
    }
}

def copyFiles( downstreamWkspc, upstreamWkspc ) {
    dir("$downstreamWkspc") { 
        bat """
            @set prompt=\$g\$s
            dir
            xcopy /f *.* \"$upstreamWkspc\\\"
            dir \"$upstreamWkspc\"
        """
    }
}

Template for downstream projects SO-69680107-2 , SO-69680107-3 , SO-69680107-k :

// Pipeline project: SO-69680107-X
pipeline {
    agent any
    stages {
        stage('Stage X') {
            steps {
                sh 'set +x; echo "Step X" | tee SO-69680107-X.log; date; sleep 3; date'
            }
        }
    }
}