Hi @baldvin_thor ,
Yes, it should be possible in Graph Builder to do what you want. Below is a screenshot showing how that can be done. I'm using the Big Class.jmp file as an example. I am graphing height and weight vs age (turned age into a continuous variable, not ordinal). Anyway, in the GB control panel under line of fit, there is a checkbox for Confidence fit. You can uncheck this (as I did for height vs age) and the confidence interval goes away.
You have to have the y variables on their own axis. If they share an axis as below, then it turns off the CI for BOTH.
Hope this helps!,
DS