OK so my above post is part correct.
I'm using CPS 2 138.245 so not much newer than yours.
Go to Configuration -> General -> Control Buttons
Assign your P1 button (either short or long) to One Touch Access 1.
Scroll down a bit to One Touch Access settings.
For One Touch Access 1, click in the field for Mode and change to Home Revert.
Then click in the field for Channel Zone and choose your preferred zone.
Then click in the field for Channel and choose your preferred channel.
