square-plus from coolicons in Line with regular corners. add, new, create, insert, expand, increase, box, rectangle. Other styles and corners: @coolicons/<style>/<radius>/square-plus with line, duocolor, duotone, fill or bulk and sharp or round. Leave out regular, like @coolicons/fill/square-plus, and use @coolicons/square-plus for line with regular corners.
pnpm dlx shadcn@latest add "https://coolicons.cool/r/square-plus.json"