Edit Milestone Completion Date?

Edit Milestone Completion Date?

I am a new Zoho user, and I am adding some existing project data to Zoho projects.

I have added some milestones for the project, and some of those milestones were already completed. I checked them as complete, and when doing so it sets the completion date to the date the milestone was checked as complete (today, for example).

So now I have an overdue milestone, that was actually completed on time, but I have no way to edit the completed date to before I joined Zoho, when I actually completed the milestone.

I hope this functionality can be added soon. Or, maybe it already exists, and I haven't found it?

Many thanks.