We have finally managed to get the code tag button and its tool tip changed to something more meaningful.
As you should see when composing a post in the forum the button is now:
<CODE/>
And the tool tip is:
Use code tags to format code for the forum
If it has not changed on your browser then I suggest that you restart it.
I will update the forum instructions in due course.
My thanks to @Ballscrewbob , @UKHeliBob and @pert , and the wonderfully helpful people at Discourse for their help in getting this done.
EDIT
No, I have not updated the forum instructions yet, I am on holiday and I don't want to do it using a phone or tablet. I will do it when I get home and can use my PC, probably first week in April.