With the following pipeline

pipeline {
    agent any
    stages {
        stage('Wait') {
            parallel {
                stage('First') {
                    steps {
                        sleep 20
                    }
                }
                stage('Second') {
                    steps {
                        sleep 40
                    }
                }
            }
        }
    }
}

I can’t click on the second (bottom) bubble in the visualization. When I do, the highlighted bubble remains the first (top). Nevertheless, a no-op entry is added to the browser history stack (so if I futilely click ten times on the second bubble, I have to click back eleven times to actually go back).

Once the first stage completes, I can click on the second.