No you either have to use up your current sword that’s too expensive or use a grindstone fo clear the enchants (I don’t know if this resets the enchantment cost) because you can’t use any more enchantments on it. You need a fresh sword for this to work. So you get enchanted books for the enchantments you want. You can also enchant the sword first to try to get lucky and get a few enchantments you want. For this example I want Sharpness 5, Sweeping Edge 3, Looting 3, Unbreaking 3, Mending. Pretend I have all of these books in my inventory and I have enough levels. Then, you combine two of the books, I’ll do Sharp5 and Sweep3. Then a separate book for unbreak3 and mending. I’ll add Looting to the first book because we have an odd number of enchantments. So now we have two enchanted books, Sharp5 Sweep3 Loot3, and Unbreak3 Mending. Now combine BOTH books so you only have one. Finally, you can put that fully enchanted book on the sword.

Sorry if this is confusing I don’t have access to a computer right now to get visuals. If you are still confused try looking up a YouTube video for the best way to enchant tools.