Change the key or the capo for the chart you are looking at, without retyping the song.
Tap the floating Key button. Change Key opens beside the button.
The same key and capo are on Edit Song as Current Key and Capo. Changing the key there asks Transpose chords? with Leave As-Is and Transpose.
Nashville numbers, in Song Format, displays numbers in place of chord letters on the displayed chart. The stored chart stays in letter chords.
A pedal or touch zone can run Transpose Up, Transpose Down, Capo Up, and Capo Down one step at a time.