Have you tried symbolic links on your MAC? It has been a while since I have
done much with my older one...
But I know Ubuntu and had same issue with opening sketches through a symbolic link, and I believe I tried it as well with my MAC...
For example have an external drive plugged in with some directories and create a symbolic link to it..
ln -s (path of other directory)
For the fun of it, I may try to verify it again later today...