Open the item and click Convert to Subrecipe (on an ingredient) or Convert to Ingredient (on a sub-recipe) in the header, then confirm "Are you sure you want to convert this item?" in the pop-up. Conversion only flips the item's type: all fields are kept, and you are redirected to the item under its new section (/admin/subrecipes/ID or /admin/ingredients/ID). The Convert button needs a Seed plan or higher. Note that if you open a sub-recipe through the Ingredients URL (or vice versa) Sprwt automatically redirects you to the correct section.