When you want to see a history of position hierarchy you need to access Position/ Manage changes/ Positions hierarchies. But currently you can find there only overview of managers' POSITIONS without WORKERS=NAMES of managers assigned in that time.

As time passes, an opaque history develops.

It is important not only to know the history of position hierarchy, but also the history of supervising workers=names hierachy as workers on positions can change and when a longer history is created it is not clear who was the manager in that time.