You control transposition by adding and editing transposition points on the Transposition track. Working with transposition points is similar to working with automation points in the Tracks area.
Command-click the transposition curve (line) at the point where you want to transpose the project.
Drag the transposition point up or down to a new value.
As you move the transposition point, a help tag appears, showing the current transposition value.
Click the transposition point, then press Delete.
You can copy transposition points using the standard Copy and Paste operations or by Option-dragging them.
You can also copy or move multiple transposition events simultaneously, which can be useful for repeated project sections.