For the stat badges only, add a new checkbox in the Onyx badge details (tier 4 in backend) to mark a badge with the Recursion wings (double onyx). Should probably still be a category toggle as in theory the Goruck badges can also be double onyx (but I don't think anyone got that far yet) and enabling it for all Onyx badges regardless of category would mean that you could mark the birthday badges as well.
For the stat badges only, add a new checkbox in the Onyx badge details (tier 4 in backend) to mark a badge with the Recursion wings (double onyx). Should probably still be a category toggle as in theory the Goruck badges can also be double onyx (but I don't think anyone got that far yet) and enabling it for all Onyx badges regardless of category would mean that you could mark the birthday badges as well.