Someone commented on my issue report that they have an error when trying to start the Arduino IDE in portable mode on macOS:
Arduino cannot run because it could not create a folder to store your sketchbook.
Do either of you have an idea about that problem?
It seems like it could be a permissions issue because the default sketchbook location (at least on Windows, IDE 1.8.5) is inside the portable folder so it needs to create the folder there.
I find that on Window 10 if I have the IDE installed under the Program Files (x86) folder I get the same message unless I do a "Run as Administrator". Even after the folder is created, when I start the IDE it just dies after the splash screen unless it's run as administrator. I didn't have that happen on Windows 7 that I can recall.
Is there a "Run as Administrator" equivalent on macOS? Interestingly they also had no luck with sudo open Arduino.app.