Just copying some correspondence with Mona here for the sake of completeness:
From Mona:
Steve,
The Help was not updated. To insert a program or a new program line, use ] as in Mathcad 14.
Go to Math tab > Operators and you�ll see the programming operators listed.
My reply:
Thanks Mona,
But this is still a step backwards from M14. With M14, I can have the Programming Toolbox right next to whatever program I'm working on, and it's a one-click operation to insert a new operator. Now I have to go to the Ribbon and it's a two-click operation.
Couldn't there at least be a simile to the old Toolbox that appears when I work in a program? Ironically, because Prime is less "mouse friendly" on this front than M14, I've started to learn the keyboard shortcuts for programming (which I didn't need in M14). Yet another instance of the Ribbon being a step backwards in usability.