Given the following pipeline

stage "Stage 1"
stage ("Trigger jobs") {
    parallel(
        downstream1: {
            build 'downstream1'
        },
        downstream2: {
            build 'downstream2'
        }
    )
}

and downstream1/downstream2 being just "sleep 300"

See the rendered flow in attachment: the "Building downstream1" and "Building downstream2" are not rendered within the parallel steps.