Actually, you must use the file name in “hard drive mode” 
But the path is not absolute, instead it is relative to the macros root folder. The root folder is specified in the XModule settings page.
So instead of
macro=“file://///Mac/PathToMacroJSON/uivision/macros/macroname.JSON”
this should work
macro="macroname.JSON”
assuming
Mac/PathToMacroJSON/uivision/ is your root folder.
See also here: Error Can't find macro with name "name" when run command line - #5 by admin