How can I get Windows to display the metadata I enter into .wav files?
This is Windows-specific so I started a new topic in the Windows board for you.
Assuming you are using the latest Audacity 2.0.6 from http://audacityteam.org/download/windows then the seven standard tags always listed in Audacity’s Metadata Editor are exported in WAV files as both ID3 and LIST INFO tags. See http://wiki.audacityteam.org/wiki/WAV#Metadata.
Windows reads the LIST INFO WAV tags, not ID3. If you are asking about showing the tags in columns in Windows Explorer, you can choose columns to display by right-clicking over a column. Not all tags may be supported in columns and this may vary with different versions of Windows (you did not say which version of Windows you have).
dBpoweramp has Windows shell integration for metadata tags so could be used to add any tags to Windows Explorer that may be missing. The application is free as long as you don’t want to encode MP3 files after the trial period ends.
Is it possible to display non-standard characters?
If I enter umlauts, for example, Windows formats them to regular letters. If I enter Japanese characters, they’re left blank.
We can’t see your computer and this is the Audacity Forum, not a Microsoft Forum. If you are not prepared to state your version of Audacity, version of Windows, what Region and Language format Windows is in, and exactly where you are looking in Windows for the metadata, then we can’t answer your questions.
However from personal experience dBPowerAmp (as one example) has full integration into the Windows shell and should ensure that Explorer and Windows Properties sheets (right-click over a file) will display metadata properly.