I've searched high and low for how to do this, and kind of managed using the "Transpose" settings menu, under Preferences. There is an option there for transposing the song after each chorus that's played. It took time to load after each chorus, though, so it kind of broke up the rhythm. I don't think that's the right tool, so I'll ask some colleagues who are more experienced.

In the meantime, I also found an old forum post with this workaround that might do the trick. Thanks to Pietro who posted it originally.

Originally Posted By: Nome
OK well here's a work around I just tried:
If you select the chords you have, then copy them, you can now transpose the song on screen down a 4th in the usual way, then paste the copied version on the end & you have a chart in 2 keys. Now copy all again but transpose the screen up a tone then paste the other at the end. Doesn't take long to cover the cycle of all 12 keys, remember there's a bit of length/arrangement setting adjustment too. A bit awkward but doable.
regards,
Pietro