Making a desktop shortcut icon on the Mac is pretty easy. Open up the AppleScript script editor and make a script like this:
do shell script “/Applications/Firefox.app/Contents/MacOS/firefox-bin -P Developer -no-remote &”
Then save as an application on the desktop. Done.
This example shows how to pass parameters from AppleScript. In particular, it shows how to open a 2nd Firefox window with the “Developer” profile by passing some command line parameters from AppleScript.