We have some of our projects broken out into repeatable actions. E.g. we have the same action/sub-actions for multiple different countries where we are rolling out our product. We may learn later in the project planning exercise that we might actually want to add one more sub-action to every repeatable action (in the example above, that would be adding another sub-action to all of our country specific actions). This happens all the time because, as you know, projects are dynamic. Rather than me changing the template, deleting the old sub-actions for each action and then re-adding the template, I just want to go the template, make my changes there, and it then those changes apply to all actions where the sub-action template was used.