Is there an app that can discount shipping based on sales automatically?

So I have multiple categories of products, each with its own shipping profile and within each profile are 7 territories and three shipping brackets for each. So a lot of variance. This is all because I use a dropshipper with a terribly complex shipping profile themselves, due to global distribution locations.

What I would like to achieve is an automated discount on shipping based on the cart value, which ideally applies a discount on whichever shipping speed they choose.

I don’t want the customer to know a discount code to enter, so I don’t believe the standard codes will work.

I could use the conditions in the shipping profiles to offer free shipping after a certain amount spent, but as you can see this would be time-consuming, not just to enter but to manage due to all the profile options.

Is there an app that can manage this task for me?

I’ve yet to find one but have the same issue. I’m unsure why Shopify don’t just allow free shipping discount codes to be automated. If I could do this it would allow me to convert more sales in the UK as it is i have to go into the shipping table for one of my suppliers every day as they insist on pushing updated shipping tables every day.