Action and Acton Reasons

On the Position Details page (Workforce Structure / Position Details ) there is action button. One of the actions available is Duplicate Position. When I select that option, there are view Action Reasons available. I need to add a new action reason for the Duplicate Position action. I can't find anywhere the action Duplicate Position nor actions reasons assigned to it in the set up. I looked in Configurate Actions, Manage Actions, Descriptive Flexifields. Can anyone assist? Thank you