To get back to Matlab, you’ll just be using your mouse for a minute. Ignore the keyboard temporarily.
Click on the little white arrow on the left side at the equator of the window.
Clicking this will open the options for the VNC window.
Click on the “A” button. When selected it will turn a darker gray than the rest of the options.
This will expand a subset of additional options.
Highlight the Alt button and make sure it’s selected. (It will also turn darker gray when selected).
Your selections should now look like the graphic on the left.
Now click the tab button. It looks like a left and right arrow and is shown to the left.
You should now see a Matlab Icon in the middle of your VNC window. Click that.
This should bring your Matlab program back up and active in your window.