Macbook: reduce usable screen area

In OS X you can change the underscan/overscan in the preferences. It wont be perfect as the setting can only change the size of the display not the position but it may help in the usability of the computer. https://support.apple.com/en-us/HT202763

You may also be able to use an external program such as DisplayConfigX if it is supported by your operating system. http://www.3dexpress.de/#Overscan

Hope this helps until you can get a more permanent solution.