It is not under "Conductor Impedance" tab. It is on "Differential Layer" panel under "Differential Pairs" tab in Saturn PCB.
If you have time I recommend you to simulate the transmission line with OpenEMS or a similar tool. The text books and calculators are okay for theoretical formulas but they sometimes differ a lot from practical results. You may need to consider PCB structure, epoxy, air, plastic enclosure, track geometries etc. Think about a 4-layer PCB, having core, prepregs and solder mask layers having different dielectric constant. But it may be too much an effort if this is just a track connecting a connector with an IC in short length.