@
Januz - Have you tried adding an alias file that references the supporting information folder.
My understanding is that OS/X alias files are similar to Windows shortcut (.lnk) files. Because they are operating system objects rather than file system objects (a'la symlinks, hardlinks etc) the OS can keep track if them if they are moved etc see
http://en.wikipedia.org/wiki/Alias_%28Mac_OS%29
The only way I've found to get a Windows "shortcut to a folder" file into calibre is via the calibre command
http://manual.calibre-ebook.com/cli/calibre.html, this adds the .lnk file as a book which I then Merge with the target book.
Fortunately the Windows Send To 'feature' maps to the calibre command line. So I 'right click' the supporting folder, select Create Shortcut, 'right click' the shortcut just created, select Send To->calibre. Then in calibre I merge the book just added (ie the .lnk file) into the target book. BTW I don't actually 'right click', I tap the menu key instead.
If the supporting files are 'static' I bundle them into a 7zip archive and add that to the book, but if they are dynamic or volatile then I use the .lnk file - sometimes I use both.
BR