New Promotion - Add Conditions?

Does anyone know how to add to the promotions “conditions” list ?

I want to add things like STOCK TOTAL or IN STOCK

With STOCK TOTAL I would like to build a promo where if I have more then one of an item the price is discounted by 10%, more then 2 discount 20% etc.

I am afraid, there is no such ability. Additional code modifications are required

we are also at your service.