🚀 go-pugleaf

You could use the command line (Terminal.app)

Assuming you have a folder INX on your desktop, with a file test.idml

This will extract the IDML into a folder "test":
unzip /Users/dave/Desktop/INX/test.idml -d /Users/dave/Desktop/INX/test

In OSX terminal.app you can use drag&drop instead of typing file names.
The option "-d" specifies the output folder. If you omit that, all the archive files will end up in your home directory.

This will rebuild the IDML:

cd /Users/dave/Desktop/INX/test
zip -r ../test2.idml *

The cd into the folder is required because this way the files will have the correct relative paths.
The option "-r" means recursive - add also the files contained within folders.

If you have the oXygen XML editor, go to Preferences/Archive, there add an entry for the ".idml" extension. Then oXygen can open IDML without going thru the unzip/zip cycle.

Dirk