Sorry, William, I haven't tried to either edit content or move the text boxes during the exam, but from what I can see on PearsonVUE practice whiteboard it doesn't look like any of these is possible.
Song, before starting the exam you are asked to close any other application running on your computer. Once you launch the PearsonVUE software, it takes full control of your computer, so you cannot exit the full screen mode nor access any other application, including the calculator on your computer. Instead, you will have access to the built-in calculator (and whiteboard) included in the application for your exam.
Gabriella