You can program a button to accomplish the centrex transfer with one touch.
On the button programming
pressing speaker will substitute for the recall, hold is a pause, you can also use these buttons in a speed dial as well to subsitute for recall and pause. # on an analog I believe is the request for a speed dial, followed by the speed dial code. Play with how many pauses and where you need them. If memory serves me
F00 =Feature 00
left intercom (not sure you need this intercom)
speaker
hold
9
hold
5551212 =telephone number
F00
to program a button that you can while on the call press it and then wait to hear it dial, then hang up.
From ext 10 or 11
F00
Feature
699 =speed dial code number
speaker
hold
9
hold
5551212 =telephone number
F00
For a speed dial, again play with the number of pauses, you will need.
Play with it a bit and test it, I am sure I am not far off on the exact sequence of speaker and hold buttons. The hold pauses to give the time to process the recall, and the 9 to be processed for the centrex feature to grab dial tome again.
You do not always get what you pay for, but you never get what you do not pay for.