From your screenshot, you are creating a Line and stacked column chart, which is a combo chart. The combo chart in Power BI Desktop only allows one field in Column Value section when you have column series, and as your post, once you add multiple fields in Column Value section, you are not able to add column series. A similar idea about this issue has been submitted in this link, please vote it up.
If you create basic Stacked column chart, the screenshot should be as follows. Similarly, Power BI Desktop only allows one field in Value section when you have Legend, once you add multiple fields in Value section, you are not able to add Legend. Please vote the idea in my original reply.
In your scenario, you would need to create two charts side by side with each one has different field in Value section and has same Legend.
Thanks, Lydia Zhang
Community Support Team _ Lydia Zhang If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.