How can I setup my Macbook Pro (2017) & Parallels to use all function keys?
Problem solved. In my case, I turned off the F11 and F12 function key usage.  Specifically, I had to go to System Preferences > Keyboard.  From there, select the Shortcuts tab, and then select "Mission Control" from the left-hand list.

Within the Mission Control shortcuts, disabling Show Desktop and Show Dashboard restored F11 and F12 key-usage in Parallels.  I'm not sure what's special about these keys and why the others seem to work without issue, even though they are assigned as Shortcut keys.  Regardless, this fixed my issue.