I need to Sort/Group By Two Different Date Fields

The simplest way is to have two separate reports.

But if you really want to have 1 report then you need to have two records to chart.  To do that you would need to have a child table on the Patient table and use automations to maintain the children.

Basically you would have an Automation that would trigger whenever a Patient is created or modified and either of those dates change, to delete the existing child records  and then add them back.