Ok, so that means that they work essentially the same, except that a full scale turn in either direction for the mode 1 makes a full scale rich or lean, whereas the mode 9 is in a much smaller increment, but still proportional to the amount the knob is turned, just not as much as in mode 1.

Not quite.  In mode 1 the mixture is changed in a step equal/proportional to the position of the Program Value knob. Just push the store button once – repeated pushing of the store button does nothing more – unless you reposition the Program Value knob. It took me a long time to get that right.

You have mode 9 right – repeated pushes of the Store button will step the mixture.

Mode 5 is used on my 3-rotor to adjust the mixture of rotor 2, so I can adjust EGTs on 1 & 2 to be the same as 3. Not needed on 2-rotor.