Here’s a workaround:
- Activate Add to selection.
- Select the far left note.
- Scroll over all the way to the far right side.
- Switch to Extend selection.
- Click on the far right note.
That should work, I just tried it on my iPad.
Another solution is:
- Activate Extend selection.
- Select the far left note.
- Open the Jump Bar, type “Go to bar”, and type in your last bar number.
- Select the last note.