A "service" product isn't a separate type — it's a fixed-price product with the price left open, so your team sets it at the point of sale. Use it for services or anything priced case-by-case.
How to set it up
Go to Products and click + Add Product.
On the Fixed Price tab, add the image, Product Title and (optional) a default Price.
Tick Make this a service product — you'll be able to edit the price when creating a transaction.
Choose the Assigned Locations and any Tags.
Click Create Product.
When your team sells this product, they enter or adjust the price for that sale. See also Add a fixed-price product.