Q: Is it possible to change the key within the song? So, for example, have the verse in "C major" and the chorus in "E major"?
A: Unfortunately, not directly. Though, you can add chords of a different key or create your own chords, which are part of a different key. Also, as a workaround, you can rotate the wheel during playback.
Long-term, I'm planning to add the possibility to select a different key/mode for each part.