I'd like to add my voice to support the OP's request. It would be wonderful if the "relationship calculator allowed you to click on a particular relationship when many are shown, and then generate a relationship chart, detailing that particular relationship."
I'm working with an island-based, endogamous population that has lots of consanguinity. It's very common to have the Relationship Calculator show 2, 3 or even 4 relationships between two individuals. Unfortunately, as the OP points out, a Relationship Chart can only be created for the closest relationship. This is a major problem for me. I've spent hours using Photoshop to create Relationship Charts for the other relationships.
Please accept my plea for modifying the Relationship Charting feature so that it can handle multiple relationships. Thanks.