Legend in a graph plotting two measures

Hi All!

To explain a bit: I have a chart with time on the x-axis and two measures on the y-axis: the real price trend of a product and the indexed price trend of a product. So, when you click on one product, you see two lines. Now, I want to use a legend in the chart so that you can also click on two products, and then see four lines in the chart. However, the program does not accept this. If I create a chart with only the real price over time or only the indexed price over time, I can apply a legend. Can I solve this? Can you add a legend to a chart where multiple values are plotted?

Hopefully it is clear. Please let me know if you need more info inorder to help.

Thank you so much in advance for helping!

Have a good weekend.

Kind regards,

Fleur