A US reseach study says that coffeee grounds are good as a soil conditioner but do not act as a fertiliser. A bit like adding sharp sand, gypsum, grit etc., stopping the soil from clagging up, improving drainage etc.. However, coffee grounds arw acidic, so are best used lightly. I compost mine.
I would not use coffee grounds on seedlings. Seed compost has practically no fertilizer as it can scorch tiny seedlings, as can acidic grounds. In fact, you can grow seedlings well in perlite or vermiculite, which are totally inert. the seed capsule has all the nutreients needed until the seedling is ready to prick out at the first true leaf stage.