Have you tried using @-escapes in the dictionary word? I.e. @{abcd} where abcd is a Unicode code point.
I haven’t so it might not work.
I didn’t manage to make those work, however moving those parts of code from the Language.w file to the extension .i7x file, solved this issue.
Include (-
...
Constant BY__WD = 'από';
...
-) replacing "Vocabulary".
While I’m not sure if it’s the ideal method for extensions, I’m happy with the results so far since it enables me to test commands and phrases properly.