How to make a discount or apply a coupon directly in the cart template?

Question

1C-Bitrix

How many did not look for examples, advice, solutions in the internet and did not understand how to implement this.
A certain amount is formed in the basket template, it must be applied to the final price of the basket as a discount for an order that has not yet been formed.
I looked in the direction of the coupon, but coupons are not generated with a price, well, or I don’t know how.
I looked in the direction of the discount, but the discount goes to the product, and not to the entire basket.

I'm confused, how can I make and apply a simple cart discount?

I think now I’ll get into the database and directly change the values, but figs there, there is a base with such occurrences that the devil will break his leg.