Solution for trackpad handwriting
Through many updates of Mac OS trackpad handwriting has been a continuing problem. I finally worked out a solution. Trackpad handwriting will not appear on a desktop which is not the most recent desktop to use full screen viewing of a window. Every other window will fail to open the handwriting window. The solution is to open any window on that desktop to full screen. Then the handwriting window will appear and work normally, even if you take the window you openned out of full screen.