How can I run two instances (or equivalent) of Slic3r on OS X? I am modifying some Slic3r config parameters and comparing the results.  How can I have two instances (or equivalent: I would like to see two model windows with their associated configuration screens) of Slic3r at the same time?  I'm on OS X, but if there is a generic (e.g. within Slic3r) solution that will be preferrable.
You could duplicate the application by clicking on the application and pressing Command (⌘) + D, and then run both - although I'm not sure if that would mess with the preferences. I haven't fully tested it, but both instances opened up and worked, seemingly ok.



You could even rename them to something other than "Slic3r" and "Slic3r copy" to remind you which application is slicing which model, for example:


"TestCube" and "Benchy", or;
"Slic3r-TestCube" and "Slic3r-Benchy", or whatever. 


However, Mark's answer seems much more elegant.