I read on one of the posts how the volume of a performance could be adjusted within a live set slot. Can transposition be altered in the same way?
No, certainly not in the same way. Transposition is a function of the Keyboard transmitting and will globally affect things out via MIDI as well as internal. The Volume is a function of the internal tone generator.
If you wish to memorize the transposition of the Keyboard transmitting you would store that within the Performance using the Master Zone function.
And if you're thinking about using NOTE SHIFT, which addresses the internal Tone Generator, that is always a PART parameter and is again handled within the Performance on a per Part basis.