Re: Changing the key in the middle...
Here is a step-by-step (with a couple of alternatives thrown in):
1. Click on the disclosure triangle next to the word Global Tracks above the Track List.
2. You should see a selected array of Global Tracks available. However, like normal tracks they can be expanded or resized. Either click on the disclosure triangle next to the Signature track:
or position your mouse cursor over the horizontal boundary lines between the global track. You'll notice your mouse cursor turns into a resize tool.
Drag to resize the Global Track:
3. To create a key change, right-click anywhere in the Key lane to see this menu:
(Alternatively, use the Pencil tool and click in the Key lane.)
Choose "Create Key change" and you should see the Key Signature dialog window appear:
4. Once you've selected the key, click OK. And here we have the Key change in the project:
btw, you can customise the Global Tracks to view by right-clicking (control-clicking) on any Global Track to see this menu, where you can choose which ones to view and which ones to hide:
Hope this helps
p.s. There is a transposition Global track where you can transpose your project as opposed to change the Key. This might be what you were originally looking for?