The new label/filter paradigm in Opera has required me to do just a little adjustment. At some point, I deleted my Todo label, but now I want it back. The natural thing to do would be to just add a new label and name it “Todo” but this does not quite work because the icon is still the icon of a message filter, rather than of the Todo label.
To fix this, I went into my mail/index.ini folder and found the Todo label section. There, I found the entry called “Skin Image” and used “Label Todo” as the value instead of what it was, “Mail Filter.”