I have a gantry with 2 steppers one on each side my controller only has 3 stepper motor spots I'm not using z axis so I would connect the second stepper to z axis. Then I guess I go into ports and pins my issue is would I put the same numbers in the z axis as it is in x axis (example step pin 2 dir pin 3) then I guess you go to the slave axis drop down and go x axis and check the slave axis ( A , B, C,) so which one do I check there's no z axis, does it make a difference which one I check If I disable z axis will it then work if I check slave axis A?

Thanks

Then I guess I go into ports and pins my issue is would I put the same numbers in the z axis as it is in x axis (example step pin 2 dir pin 3)

No. You use whatever pin numbers that your Z axis drive uses, but you assign them to the A axis. You do not use the same pin numbers as the X.
Then, you go to ports and pins, and slave the A axis to the X axis.