How to upload the items with discounts to Pricing Pormotion?

Summary:

We need to upload 2000 items to pricing promotion.

However, we have not found any solution for uploading them.

Content (please ensure you mask any confidential information):

The customer has 2,000 items with promotional discounts that need to be imported into the system. However, we have not found any solution for uploading them. Currently, the only available method is manual entry, but given the volume of approximately 2,000 items, entering each one manually is not a practical approach.
Also, we did not find any REST API for pricing promotions. Could you lease help and provide the details how to upload the big amount of items to the pricing promotions.