How to filter an X-Axis without filtering the underlying data

Hi all!

I'm working on an HR dashboard and have run into an issue with showing turnover/retention. I'm trying to show our current leadership structure while counting terms even if the leader they reported to is no longer with us. We don't have org units so I can't just use that. I also want people to be able to look at prior dates, so I can't just lock us into the current structure.

Here you can see a sample team where Leader 2-4 was with us in July, but not in August. 

But when I try to show their bosses' (Leader 1-A) turnover it seems I either have to show all leaders who've ever been with us, or incorrectly report turnover by not including people who left under leaders who are no longer with us.

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