Hello. I hope I've reached the proper channels.
The current Japanese translation has no entry for "untitled" (ala Ctrl + N), leaving it as is. "新規ファイル" translates directly as "new file" but is standard in the Ctrl + N context.
Provided the value for "untitled" doesn't appear in other contexts which would be misleading (in other words, actual dependence upon the literal meaning of "having no name"), I propose changing the value for "untitled" to the more user-friendly "新規ファイル." I highly doubt any Japanese-speaking users have encountered any confusion over "untitled," but still--it feels good to uphold standards.
If, however, a literal meaning of "new file" would conflict with other uses of the untitled entry, I suggest "編集中ファイル," literally "file being operated upon."
Another possible translation, "未タイトル ("not yet titled")," does match the literal meaning of "untitled" nicely--but it sounds kind of weird.
Were I the dictator of Geany translations, I'd just go with "新規ファイル" and call it a day. You'll find the entry at line number 3,115 in file geany/po/ja.po.
Thanks for your time, and thanks for translating Geany. As a very satisfied user, I feel that everyone's doing a wonderful job.
Sincerely, Grady Martin