Graph line with parameters and filters

Hello everybody,

I'm trying to build a line graph that uses a parameter to choose the metrics applied to each testcase. Everything works fine for a test case, my problem is that in addition I want to be able to compare between multiple test cases.

This is the case of just one test case, working fine and filtering by chosen metric.

But when I select more than one test case, the graph stops working with the error in the image below. I wanted it to add newlines as per the test case.

This is the approximate graph I want to achieve:

Why am I having this problem and how can I resolve it?

https://we.tl/t-p2c8ZZRCSq

Best regards.