The Level X-Axis feature is only for the Mini 2. If you would like to level the X-axis on your Mini 1, you can do this manually. You’ll want to raise your tool head toward the top of the frame. Using a ruler or tape measure you will want measure from the top smooth rod of the X-axis to the top of the frame. Please measure on the left or the right. You can then adjust your X-axis by either turning the threaded rod or the coupler that connects the motor shaft to the threaded rod (the coupler looks like a cylinder with black stripes and is located in the green bracket above your Z-axis motors).
You’ll want to make the measurements until both sides are the same.