the FileChoosers filePatternsAllowed are limiting FileChooser usability:
a combined “*.txt;*.doc” doesn’t make sense during a “save as…” situation. Here you explicitly want to choose either one or the other.
Windows supports something like “text file: *.txt\0document file: *.doc\0\0” and this seems also be implemented using “|” at the platform abstraction in JUCE. However “|” does not work on OSX.
In a “load” situation a separated “*.txt” “*.doc” may also make sense to allow filtering for different file type. This also seems to implemented with “|”, but again will break the OSX implementation.