Fit Y by X is a specialized platform that only handles one Y and one X per analysis. The Fit Model is the platform you might need to be using, if you are looking for a mullti factor ANOVA or you may be able to get the graph you want from the Variability Chart platform
Analyze==>Quality and Process==>Variability Chart
![var1.PNG var1.PNG](https://community.jmp.com/t5/image/serverpage/image-id/23086i72AD3C8844AAB21F/image-size/large?v=v2&px=999)
If you can be more specific in what you are looking for out of the Fit Y by X, a better solution may be determined.
Jim