workflow_participants-8.x-2.x-dev/config/install/workflow_participants.settings.yml

enable_notifications: true
participant_message:
  subject: 'You have been added as workflow participant to [node:title]'
  body:
    value: "Greetings [user:name],\n\n You have been added as a workflow participant to [node:title].\n\n[node:url:absolute]"
    format: plain_text