Discount on the Line Item Level
Not really. As you have already identified, Discount items are normally used for this. They produce the mechanical advantage of being able to divert the discounted value to another GL Account. If you don’t use them, then there are various schemes possible to make “discounts”, such as using Price Levels, but all of these mechanisms will simply reduce the value of the item, i.e. the revenue posting.
If you’re ok with the “discount” simply reducing the sales price (revenue) of the item and not posting to a different account, then Price Levels are your best bet.
If you want to sales to post to a different GL Account, there are no other options than to use Discount items.
Note that if your ultimate worry if how the customer-facing invoice PDF looks (i.e. you don’t want to print out Discount lines), then you can resolve that by programming your Advanced PDF Layout to “squish” the Discount and the Item so they print out as one line only. This requires some know-how though, so maybe plan a little bit of money to hire a consultant to do it.