You can change the view mode on the running virtual machine. To switch to Full Screen or Scaled mode, go to View and select either to switch to Full Screen or Scaled Mode.
Press on Switch to change the view.
If you wanted to revert the view, follow as below, (by default, during the view switch – as above screenshot – it will notify you the key to revert the view)
• Revert Full screen, CTRL(right side of the keyboard) + F
• Revert Scaled Mode, CTRL(right side of the keyboard) + C