Piano rack Advanced

How can I re-program the outside line buttons a Merlin 410 phone system? - phone system manuals

I have the AT & T / Lucent / Avaya Merlin 410 Phone System in my office. Above left are 4 preset buttons for outside lines.
Since we have only 2 external lines, I want the keys to one of the other programs, program, so I have 2 "dead" button.

I tried following the manual, but the program is not maintained. I know I kept doing it correctly and in group 2, 5 buttons (I a 10-key receiver I use).

Can anyone tell me if this is possible, if so, how?

Thanks in advance!

-Matt